├── .circleci └── config.yml ├── .gitignore ├── LICENSE ├── README.md ├── collection.go ├── collection_test.go ├── const.go ├── dal.go ├── dal_test.go ├── db.go ├── db_test.go ├── expected ├── TestCreateDalIncorrectMagicNumber ├── TestCreateDalWithExistingFile ├── TestDeserializeCollection ├── TestDeserializeWithChildNodes ├── TestDeserializeWithoutChildNodes ├── TestFreelistDeserialize ├── TestFreelistSerialize ├── TestMetaDeserialize ├── TestMetaSerialize ├── TestSerializeCollection ├── TestSerializeWithChildNodes └── TestSerializeWithoutChildNodes ├── freelist.go ├── freelist_test.go ├── go.mod ├── go.sum ├── main.go ├── meta.go ├── meta_test.go ├── node.go ├── node_test.go ├── testutils.go ├── tx.go └── tx_test.go /.circleci/config.yml: -------------------------------------------------------------------------------- 1 | # Golang CircleCI 2.0 configuration file 2 | version: 2 3 | jobs: 4 | build: 5 | docker: 6 | - image: circleci/golang:1.17 7 | working_directory: /go/src/github.com/amit-davidson/btree 8 | resource_class: small 9 | steps: 10 | - checkout 11 | - run: 12 | name: Run tests 13 | command: | 14 | go test -v ./... -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | *.o 2 | *.a 3 | *.so 4 | .idea 5 | .vscode -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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Limitation of Liability. 601 | 602 | IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 603 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS 604 | THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY 605 | GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE 606 | USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF 607 | DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD 608 | PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), 609 | EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF 610 | SUCH DAMAGES. 611 | 612 | 17. Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # LibraDB 2 | 3 | [![made-with-Go](https://github.com/go-critic/go-critic/workflows/Go/badge.svg)](http://golang.org) 4 | [![made-with-Go](https://img.shields.io/badge/Made%20with-Go-1f425f.svg)](http://golang.org) 5 | [![MIT license](https://img.shields.io/badge/License-MIT-blue.svg)](https://lbesson.mit-license.org/) 6 | [![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg?style=flat-square)](http://makeapullrequest.com) 7 | [![amit-davidson](https://circleci.com/gh/amit-davidson/LibraDB.svg?style=svg)](https://app.circleci.com/pipelines/github/amit-davidson/LibraDB) 8 | 9 | LibraDB is a simple, persistent key/value store written in pure Go. The project aims to provide a working yet simple 10 | example of a working database. If you're interested in databases, I encourage you to start here. 11 | 12 | This database accompanies my [blog post](https://betterprogramming.pub/build-a-nosql-database-from-the-scratch-in-1000-lines-of-code-8ed1c15ed924) on how to write a database from scratch. 13 | 14 | ## Installing 15 | 16 | To start using LibraDB, install Go and run `go get`: 17 | 18 | ```sh 19 | go get -u github.com/amit-davidson/LibraDB 20 | ``` 21 | 22 | ## Basic usage 23 | ```go 24 | package main 25 | 26 | import "github.com/amit-davidson/LibraDB" 27 | 28 | func main() { 29 | path := "libra.db" 30 | db, _ := LibraDB.Open(path, LibraDB.DefaultOptions) 31 | 32 | tx := db.WriteTx() 33 | name := []byte("test") 34 | collection, _ := tx.CreateCollection(name) 35 | 36 | key, value := []byte("key1"), []byte("value1") 37 | _ = collection.Put(key, value) 38 | 39 | _ = tx.Commit() 40 | } 41 | ``` 42 | ## Transactions 43 | Read-only and read-write transactions are supported. LibraDB allows multiple read transactions or one read-write 44 | transaction at the same time. Transactions are goroutine-safe. 45 | 46 | LibraDB has an isolation level: [Serializable](https://en.wikipedia.org/wiki/Isolation_(database_systems)#Serializable). 47 | In simpler words, transactions are executed one after another and not at the same time.This is the highest isolation level. 48 | 49 | ### Read-write transactions 50 | 51 | ```go 52 | tx := db.WriteTx() 53 | ... 54 | if err := tx.Commit(); err != nil { 55 | return err 56 | } 57 | ``` 58 | ### Read-only transactions 59 | ```go 60 | tx := db.ReadTx() 61 | ... 62 | if err := tx.Commit(); err != nil { 63 | return err 64 | } 65 | ``` 66 | 67 | ## Collections 68 | Collections are a grouping of key-value pairs. Collections are used to organize and quickly access data as each 69 | collection is B-Tree by itself. All keys in a collection must be unique. 70 | ```go 71 | tx := db.WriteTx() 72 | collection, err := tx.CreateCollection([]byte("test")) 73 | if err != nil { 74 | return err 75 | } 76 | _ = tx.Commit() 77 | ``` 78 | 79 | ### Auto generating ID 80 | The `Collection.ID()` function returns an integer to be used as a unique identifier for key/value pairs. 81 | ```go 82 | tx := db.WriteTx() 83 | collection, err := tx.GetCollection([]byte("test")) 84 | if err != nil { 85 | return err 86 | } 87 | id := collection.ID() 88 | _ = tx.Commit() 89 | ``` 90 | ## Key-Value Pairs 91 | Key/value pairs reside inside collections. CRUD operations are possible using the methods `Collection.Put` 92 | `Collection.Find` `Collection.Remove` as shown below. 93 | ```go 94 | tx := db.WriteTx() 95 | collection, err := tx.GetCollection([]byte("test")) 96 | if err != nil { 97 | return err 98 | } 99 | 100 | key, value := []byte("key1"), []byte("value1") 101 | if err := collection.Put(key, value); err != nil { 102 | return err 103 | } 104 | if item, err := collection.Find(key); err != nil { 105 | return err 106 | } 107 | 108 | if err := collection.Remove(key); err != nil { 109 | return err 110 | } 111 | _ = tx.Commit() 112 | ``` 113 | -------------------------------------------------------------------------------- /collection.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import ( 4 | "bytes" 5 | "encoding/binary" 6 | ) 7 | 8 | type Collection struct { 9 | name []byte 10 | root pgnum 11 | counter uint64 12 | 13 | // associated transaction 14 | tx *tx 15 | 16 | } 17 | 18 | func newCollection(name []byte, root pgnum) *Collection { 19 | return &Collection{ 20 | name: name, 21 | root: root, 22 | } 23 | } 24 | 25 | func newEmptyCollection() *Collection { 26 | return &Collection{} 27 | } 28 | 29 | func (c *Collection) ID() uint64 { 30 | if !c.tx.write { 31 | return 0 32 | } 33 | 34 | id := c.counter 35 | c.counter += 1 36 | return id 37 | } 38 | 39 | func (c *Collection) serialize() *Item { 40 | b := make([]byte, collectionSize) 41 | leftPos := 0 42 | binary.LittleEndian.PutUint64(b[leftPos:], uint64(c.root)) 43 | leftPos += pageNumSize 44 | binary.LittleEndian.PutUint64(b[leftPos:], c.counter) 45 | leftPos += counterSize 46 | return newItem(c.name, b) 47 | } 48 | 49 | func (c *Collection) deserialize(item *Item) { 50 | c.name = item.key 51 | 52 | if len(item.value) != 0 { 53 | leftPos := 0 54 | c.root = pgnum(binary.LittleEndian.Uint64(item.value[leftPos:])) 55 | leftPos += pageNumSize 56 | 57 | c.counter = binary.LittleEndian.Uint64(item.value[leftPos:]) 58 | leftPos += counterSize 59 | } 60 | } 61 | 62 | // Put adds a key to the tree. It finds the correct node and the insertion index and adds the item. When performing the 63 | // search, the ancestors are returned as well. This way we can iterate over them to check which nodes were modified and 64 | // rebalance by splitting them accordingly. If the root has too many items, then a new root of a new layer is 65 | // created and the created nodes from the split are added as children. 66 | func (c *Collection) Put(key []byte, value []byte) error { 67 | if !c.tx.write { 68 | return writeInsideReadTxErr 69 | } 70 | 71 | i := newItem(key, value) 72 | 73 | // On first insertion the root node does not exist, so it should be created 74 | var root *Node 75 | var err error 76 | if c.root == 0 { 77 | root = c.tx.writeNode(c.tx.newNode([]*Item{i}, []pgnum{})) 78 | c.root = root.pageNum 79 | return nil 80 | } else { 81 | root, err = c.tx.getNode(c.root) 82 | if err != nil { 83 | return err 84 | } 85 | } 86 | 87 | // Find the path to the node where the insertion should happen 88 | insertionIndex, nodeToInsertIn, ancestorsIndexes, err := root.findKey(i.key, false) 89 | if err != nil { 90 | return err 91 | } 92 | 93 | // If key already exists 94 | if nodeToInsertIn.items != nil && insertionIndex < len(nodeToInsertIn.items) && bytes.Compare(nodeToInsertIn.items[insertionIndex].key, key) == 0 { 95 | nodeToInsertIn.items[insertionIndex] = i 96 | } else { 97 | // Add item to the leaf node 98 | nodeToInsertIn.addItem(i, insertionIndex) 99 | } 100 | nodeToInsertIn.writeNode(nodeToInsertIn) 101 | 102 | ancestors, err := c.getNodes(ancestorsIndexes) 103 | if err != nil { 104 | return err 105 | } 106 | 107 | // Rebalance the nodes all the way up. Start From one node before the last and go all the way up. Exclude root. 108 | for i := len(ancestors) - 2; i >= 0; i-- { 109 | pnode := ancestors[i] 110 | node := ancestors[i+1] 111 | nodeIndex := ancestorsIndexes[i+1] 112 | if node.isOverPopulated() { 113 | pnode.split(node, nodeIndex) 114 | } 115 | } 116 | 117 | // Handle root 118 | rootNode := ancestors[0] 119 | if rootNode.isOverPopulated() { 120 | newRoot := c.tx.newNode([]*Item{}, []pgnum{rootNode.pageNum}) 121 | newRoot.split(rootNode, 0) 122 | 123 | // commit newly created root 124 | newRoot = c.tx.writeNode(newRoot) 125 | 126 | c.root = newRoot.pageNum 127 | } 128 | 129 | return nil 130 | } 131 | 132 | // Find Returns an item according based on the given key by performing a binary search. 133 | func (c *Collection) Find(key []byte) (*Item, error) { 134 | n, err := c.tx.getNode(c.root) 135 | if err != nil { 136 | return nil, err 137 | } 138 | 139 | index, containingNode, _, err := n.findKey(key, true) 140 | if err != nil { 141 | return nil, err 142 | } 143 | if index == -1 { 144 | return nil, nil 145 | } 146 | return containingNode.items[index], nil 147 | } 148 | 149 | // Remove removes a key from the tree. It finds the correct node and the index to remove the item from and removes it. 150 | // When performing the search, the ancestors are returned as well. This way we can iterate over them to check which 151 | // nodes were modified and rebalance by rotating or merging the unbalanced nodes. Rotation is done first. If the 152 | // siblings don't have enough items, then merging occurs. If the root is without items after a split, then the root is 153 | // removed and the tree is one level shorter. 154 | func (c *Collection) Remove(key []byte) error { 155 | if !c.tx.write { 156 | return writeInsideReadTxErr 157 | } 158 | 159 | // Find the path to the node where the deletion should happen 160 | rootNode, err := c.tx.getNode(c.root) 161 | if err != nil { 162 | return err 163 | } 164 | 165 | removeItemIndex, nodeToRemoveFrom, ancestorsIndexes, err := rootNode.findKey(key, true) 166 | if err != nil { 167 | return err 168 | } 169 | 170 | if removeItemIndex == -1 { 171 | return nil 172 | } 173 | 174 | if nodeToRemoveFrom.isLeaf() { 175 | nodeToRemoveFrom.removeItemFromLeaf(removeItemIndex) 176 | } else { 177 | affectedNodes, err := nodeToRemoveFrom.removeItemFromInternal(removeItemIndex) 178 | if err != nil { 179 | return err 180 | } 181 | ancestorsIndexes = append(ancestorsIndexes, affectedNodes...) 182 | } 183 | 184 | ancestors, err := c.getNodes(ancestorsIndexes) 185 | if err != nil { 186 | return err 187 | } 188 | 189 | // Rebalance the nodes all the way up. Start From one node before the last and go all the way up. Exclude root. 190 | for i := len(ancestors) - 2; i >= 0; i-- { 191 | pnode := ancestors[i] 192 | node := ancestors[i+1] 193 | if node.isUnderPopulated() { 194 | err = pnode.rebalanceRemove(node, ancestorsIndexes[i+1]) 195 | if err != nil { 196 | return err 197 | } 198 | } 199 | } 200 | 201 | rootNode = ancestors[0] 202 | // If the root has no items after rebalancing, there's no need to save it because we ignore it. 203 | if len(rootNode.items) == 0 && len(rootNode.childNodes) > 0 { 204 | c.root = ancestors[1].pageNum 205 | } 206 | 207 | return nil 208 | } 209 | 210 | // getNodes returns a list of nodes based on their indexes (the breadcrumbs) from the root 211 | // p 212 | // / \ 213 | // a b 214 | // / \ / \ 215 | // c d e f 216 | // For [0,1,0] -> p,b,e 217 | func (c *Collection) getNodes(indexes []int) ([]*Node, error) { 218 | root, err := c.tx.getNode(c.root) 219 | if err != nil { 220 | return nil, err 221 | } 222 | 223 | nodes := []*Node{root} 224 | child := root 225 | for i := 1; i < len(indexes); i++ { 226 | child, _ = c.tx.getNode(child.childNodes[indexes[i]]) 227 | nodes = append(nodes, child) 228 | } 229 | return nodes, nil 230 | } 231 | -------------------------------------------------------------------------------- /collection_test.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import ( 4 | "github.com/stretchr/testify/assert" 5 | "github.com/stretchr/testify/require" 6 | "os" 7 | "testing" 8 | ) 9 | 10 | func Test_GetAndCreateCollection(t *testing.T) { 11 | db, cleanFunc := createTestDB(t) 12 | defer cleanFunc() 13 | 14 | tx := db.WriteTx() 15 | 16 | collectionName := testCollectionName 17 | createdCollection, err := tx.CreateCollection(collectionName) 18 | require.NoError(t, err) 19 | 20 | err = tx.Commit() 21 | require.NoError(t, err) 22 | 23 | tx = db.ReadTx() 24 | actual, err := tx.GetCollection(collectionName) 25 | require.NoError(t, err) 26 | 27 | err = tx.Commit() 28 | require.NoError(t, err) 29 | 30 | expected := newEmptyCollection() 31 | expected.root = createdCollection.root 32 | expected.counter = 0 33 | expected.name = collectionName 34 | 35 | areCollectionsEqual(t, expected, actual) 36 | } 37 | 38 | func Test_GetCollectionDoesntExist(t *testing.T) { 39 | db, cleanFunc := createTestDB(t) 40 | defer cleanFunc() 41 | 42 | tx := db.ReadTx() 43 | collection, err := tx.GetCollection([]byte("name1")) 44 | require.NoError(t, err) 45 | 46 | assert.Nil(t, collection) 47 | } 48 | 49 | func Test_CreateCollectionPutItem(t *testing.T) { 50 | db, cleanFunc := createTestDB(t) 51 | defer cleanFunc() 52 | 53 | tx := db.WriteTx() 54 | 55 | collectionName := testCollectionName 56 | createdCollection, err := tx.CreateCollection(collectionName) 57 | require.NoError(t, err) 58 | 59 | newKey := []byte("0") 60 | newVal := []byte("1") 61 | err = createdCollection.Put(newKey, newVal) 62 | require.NoError(t, err) 63 | 64 | item, err := createdCollection.Find(newKey) 65 | require.NoError(t, err) 66 | 67 | assert.Equal(t, newKey, item.key) 68 | assert.Equal(t, newVal, item.value) 69 | } 70 | 71 | func Test_DeleteCollection(t *testing.T) { 72 | db, cleanFunc := createTestDB(t) 73 | defer cleanFunc() 74 | 75 | tx := db.WriteTx() 76 | 77 | collectionName := testCollectionName 78 | createdCollection, err := tx.CreateCollection(collectionName) 79 | require.NoError(t, err) 80 | 81 | err = tx.Commit() 82 | require.NoError(t, err) 83 | 84 | tx = db.WriteTx() 85 | actual, err := tx.GetCollection(collectionName) 86 | require.NoError(t, err) 87 | 88 | areCollectionsEqual(t, createdCollection, actual) 89 | 90 | err = tx.DeleteCollection(createdCollection.name) 91 | require.NoError(t, err) 92 | 93 | actualAfterRemoval, err := tx.GetCollection(collectionName) 94 | require.NoError(t, err) 95 | assert.Nil(t, actualAfterRemoval) 96 | 97 | err = tx.Commit() 98 | require.NoError(t, err) 99 | } 100 | 101 | func Test_DeleteItem(t *testing.T) { 102 | db, cleanFunc := createTestDB(t) 103 | defer cleanFunc() 104 | 105 | tx := db.WriteTx() 106 | 107 | collectionName := testCollectionName 108 | createdCollection, err := tx.CreateCollection(collectionName) 109 | require.NoError(t, err) 110 | 111 | newKey := []byte("0") 112 | newVal := []byte("1") 113 | err = createdCollection.Put(newKey, newVal) 114 | require.NoError(t, err) 115 | 116 | item, err := createdCollection.Find(newKey) 117 | require.NoError(t, err) 118 | 119 | assert.Equal(t, newKey, item.key) 120 | assert.Equal(t, newVal, item.value) 121 | 122 | err = createdCollection.Remove(item.key) 123 | require.NoError(t, err) 124 | 125 | item, err = createdCollection.Find(newKey) 126 | require.NoError(t, err) 127 | 128 | assert.Nil(t, item) 129 | } 130 | func TestSerializeCollection(t *testing.T) { 131 | expectedCollectionValue, err := os.ReadFile(getExpectedResultFileName(t.Name())) 132 | require.NoError(t, err) 133 | 134 | expected := &Item{ 135 | key: []byte("collection1"), 136 | value: expectedCollectionValue, 137 | } 138 | 139 | collection := &Collection{ 140 | name: []byte("collection1"), 141 | root: 1, 142 | counter: 1, 143 | } 144 | 145 | actual := collection.serialize() 146 | assert.Equal(t, expected, actual) 147 | } 148 | 149 | func TestDeserializeCollection(t *testing.T) { 150 | expectedCollectionValue, err := os.ReadFile(getExpectedResultFileName(t.Name())) 151 | 152 | expected := &Collection{ 153 | name: []byte("collection1"), 154 | root: 1, 155 | counter: 1, 156 | } 157 | 158 | collection := &Item{ 159 | key: []byte("collection1"), 160 | value: expectedCollectionValue, 161 | } 162 | actual := newEmptyCollection() 163 | actual.deserialize(collection) 164 | 165 | require.NoError(t, err) 166 | assert.Equal(t, expected, actual) 167 | } 168 | -------------------------------------------------------------------------------- /const.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import "errors" 4 | 5 | const ( 6 | magicNumberSize = 4 7 | counterSize = 4 8 | nodeHeaderSize = 3 9 | 10 | collectionSize = 16 11 | pageNumSize = 8 12 | ) 13 | 14 | var writeInsideReadTxErr = errors.New("can't perform a write operation inside a read transaction") -------------------------------------------------------------------------------- /dal.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import ( 4 | "errors" 5 | "fmt" 6 | "os" 7 | ) 8 | 9 | type pgnum uint64 10 | 11 | type Options struct { 12 | pageSize int 13 | 14 | MinFillPercent float32 15 | MaxFillPercent float32 16 | } 17 | 18 | var DefaultOptions = &Options{ 19 | MinFillPercent: 0.5, 20 | MaxFillPercent: 0.95, 21 | } 22 | 23 | type page struct { 24 | num pgnum 25 | data []byte 26 | } 27 | 28 | type dal struct { 29 | pageSize int 30 | minFillPercent float32 31 | maxFillPercent float32 32 | file *os.File 33 | 34 | *meta 35 | *freelist 36 | } 37 | 38 | func newDal(path string, options *Options) (*dal, error) { 39 | dal := &dal{ 40 | meta: newEmptyMeta(), 41 | pageSize: options.pageSize, 42 | minFillPercent: options.MinFillPercent, 43 | maxFillPercent: options.MaxFillPercent, 44 | } 45 | 46 | // exist 47 | if _, err := os.Stat(path); err == nil { 48 | dal.file, err = os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0666) 49 | if err != nil { 50 | _ = dal.close() 51 | return nil, err 52 | } 53 | 54 | meta, err := dal.readMeta() 55 | if err != nil { 56 | return nil, err 57 | } 58 | dal.meta = meta 59 | 60 | freelist, err := dal.readFreelist() 61 | if err != nil { 62 | return nil, err 63 | } 64 | dal.freelist = freelist 65 | // doesn't exist 66 | } else if errors.Is(err, os.ErrNotExist) { 67 | // init freelist 68 | dal.file, err = os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0666) 69 | if err != nil { 70 | _ = dal.close() 71 | return nil, err 72 | } 73 | 74 | dal.freelist = newFreelist() 75 | dal.freelistPage = dal.getNextPage() 76 | _, err := dal.writeFreelist() 77 | if err != nil { 78 | return nil, err 79 | } 80 | 81 | // init root 82 | collectionsNode, err := dal.writeNode(NewNodeForSerialization([]*Item{}, []pgnum{})) 83 | if err != nil { 84 | return nil, err 85 | } 86 | dal.root = collectionsNode.pageNum 87 | 88 | // write meta page 89 | _, err = dal.writeMeta(dal.meta) // other error 90 | } else { 91 | return nil, err 92 | } 93 | return dal, nil 94 | } 95 | 96 | // getSplitIndex should be called when performing rebalance after an item is removed. It checks if a node can spare an 97 | // element, and if it does then it returns the index when there the split should happen. Otherwise -1 is returned. 98 | func (d *dal) getSplitIndex(node *Node) int { 99 | size := 0 100 | size += nodeHeaderSize 101 | 102 | for i := range node.items { 103 | size += node.elementSize(i) 104 | 105 | // if we have a big enough page size (more than minimum), and didn't reach the last node, which means we can 106 | // spare an element 107 | if float32(size) > d.minThreshold() && i < len(node.items)-1 { 108 | return i + 1 109 | } 110 | } 111 | 112 | return -1 113 | } 114 | 115 | func (d *dal) maxThreshold() float32 { 116 | return d.maxFillPercent * float32(d.pageSize) 117 | } 118 | 119 | func (d *dal) isOverPopulated(node *Node) bool { 120 | return float32(node.nodeSize()) > d.maxThreshold() 121 | } 122 | 123 | func (d *dal) minThreshold() float32 { 124 | return d.minFillPercent * float32(d.pageSize) 125 | } 126 | 127 | func (d *dal) isUnderPopulated(node *Node) bool { 128 | return float32(node.nodeSize()) < d.minThreshold() 129 | } 130 | 131 | func (d *dal) close() error { 132 | if d.file != nil { 133 | err := d.file.Close() 134 | if err != nil { 135 | return fmt.Errorf("could not close file: %s", err) 136 | } 137 | d.file = nil 138 | } 139 | 140 | return nil 141 | } 142 | 143 | func (d *dal) allocateEmptyPage() *page { 144 | return &page{ 145 | data: make([]byte, d.pageSize, d.pageSize), 146 | } 147 | } 148 | 149 | func (d *dal) readPage(pageNum pgnum) (*page, error) { 150 | p := d.allocateEmptyPage() 151 | 152 | offset := int(pageNum) * d.pageSize 153 | _, err := d.file.ReadAt(p.data, int64(offset)) 154 | if err != nil { 155 | return nil, err 156 | } 157 | return p, err 158 | } 159 | 160 | func (d *dal) writePage(p *page) error { 161 | offset := int64(p.num) * int64(d.pageSize) 162 | _, err := d.file.WriteAt(p.data, offset) 163 | return err 164 | } 165 | 166 | func (d *dal) getNode(pageNum pgnum) (*Node, error) { 167 | p, err := d.readPage(pageNum) 168 | if err != nil { 169 | return nil, err 170 | } 171 | node := NewEmptyNode() 172 | node.deserialize(p.data) 173 | node.pageNum = pageNum 174 | return node, nil 175 | } 176 | 177 | func (d *dal) writeNode(n *Node) (*Node, error) { 178 | p := d.allocateEmptyPage() 179 | if n.pageNum == 0 { 180 | p.num = d.getNextPage() 181 | n.pageNum = p.num 182 | } else { 183 | p.num = n.pageNum 184 | } 185 | 186 | p.data = n.serialize(p.data) 187 | 188 | err := d.writePage(p) 189 | if err != nil { 190 | return nil, err 191 | } 192 | return n, nil 193 | } 194 | 195 | func (d *dal) deleteNode(pageNum pgnum) { 196 | d.releasePage(pageNum) 197 | } 198 | 199 | func (d *dal) readFreelist() (*freelist, error) { 200 | p, err := d.readPage(d.freelistPage) 201 | if err != nil { 202 | return nil, err 203 | } 204 | 205 | freelist := newFreelist() 206 | freelist.deserialize(p.data) 207 | return freelist, nil 208 | } 209 | 210 | func (d *dal) writeFreelist() (*page, error) { 211 | p := d.allocateEmptyPage() 212 | p.num = d.freelistPage 213 | d.freelist.serialize(p.data) 214 | 215 | err := d.writePage(p) 216 | if err != nil { 217 | return nil, err 218 | } 219 | d.freelistPage = p.num 220 | return p, nil 221 | } 222 | 223 | func (d *dal) writeMeta(meta *meta) (*page, error) { 224 | p := d.allocateEmptyPage() 225 | p.num = metaPageNum 226 | meta.serialize(p.data) 227 | 228 | err := d.writePage(p) 229 | if err != nil { 230 | return nil, err 231 | } 232 | return p, nil 233 | } 234 | 235 | func (d *dal) readMeta() (*meta, error) { 236 | p, err := d.readPage(metaPageNum) 237 | if err != nil { 238 | return nil, err 239 | } 240 | 241 | meta := newEmptyMeta() 242 | meta.deserialize(p.data) 243 | return meta, nil 244 | } 245 | -------------------------------------------------------------------------------- /dal_test.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import ( 4 | "github.com/stretchr/testify/assert" 5 | "github.com/stretchr/testify/require" 6 | "os" 7 | "testing" 8 | ) 9 | 10 | func createTestDAL(t *testing.T) (*dal, func()) { 11 | fileName := getTempFileName() 12 | dal, err := newDal(fileName, &Options{ 13 | pageSize: testPageSize, 14 | }) 15 | require.NoError(t, err) 16 | 17 | cleanFunc := func() { 18 | err = dal.close() 19 | require.NoError(t, err) 20 | err = os.Remove(fileName) 21 | require.NoError(t, err) 22 | } 23 | return dal, cleanFunc 24 | } 25 | 26 | func TestCreateAndGetNode(t *testing.T) { 27 | dal, cleanFunc := createTestDAL(t) 28 | defer cleanFunc() 29 | 30 | items := []*Item{newItem([]byte("key1"), []byte("val1")), newItem([]byte("key2"), []byte("val2"))} 31 | var childNodes []pgnum 32 | 33 | expectedNode, err := dal.writeNode(NewNodeForSerialization(items, childNodes)) 34 | require.NoError(t, err) 35 | 36 | actualNode, err := dal.getNode(expectedNode.pageNum) 37 | require.NoError(t, err) 38 | 39 | assert.Equal(t, expectedNode, actualNode) 40 | } 41 | 42 | func TestDeleteNode(t *testing.T) { 43 | dal, cleanFunc := createTestDAL(t) 44 | defer cleanFunc() 45 | 46 | var items []*Item 47 | var childNodes []pgnum 48 | 49 | node, err := dal.writeNode(NewNodeForSerialization(items, childNodes)) 50 | require.NoError(t, err) 51 | assert.Equal(t, node.pageNum, dal.maxPage) 52 | 53 | dal.deleteNode(node.pageNum) 54 | 55 | assert.Equal(t, dal.releasedPages, []pgnum{node.pageNum}) 56 | assert.Equal(t, node.pageNum, dal.maxPage) 57 | } 58 | 59 | func TestDeleteNodeAndReusePage(t *testing.T) { 60 | dal, cleanFunc := createTestDAL(t) 61 | defer cleanFunc() 62 | 63 | var items []*Item 64 | var childNodes []pgnum 65 | 66 | node, err := dal.writeNode(NewNodeForSerialization(items, childNodes)) 67 | require.NoError(t, err) 68 | assert.Equal(t, node.pageNum, dal.maxPage) 69 | 70 | dal.deleteNode(node.pageNum) 71 | 72 | assert.Equal(t, dal.releasedPages, []pgnum{node.pageNum}) 73 | assert.Equal(t, node.pageNum, dal.maxPage) 74 | 75 | newNode, err := dal.writeNode(NewNodeForSerialization(items, childNodes)) 76 | require.NoError(t, err) 77 | assert.Equal(t, dal.releasedPages, []pgnum{}) 78 | assert.Equal(t, newNode.pageNum, dal.maxPage) 79 | } 80 | 81 | func TestCreateDalWithNewFile(t *testing.T) { 82 | dal, cleanFunc := createTestDAL(t) 83 | defer cleanFunc() 84 | 85 | metaPage, err := dal.readMeta() 86 | require.NoError(t, err) 87 | 88 | freelistPageNum := pgnum(1) 89 | rootPageNum := pgnum(2) 90 | assert.Equal(t, freelistPageNum, metaPage.freelistPage) 91 | assert.Equal(t, rootPageNum, metaPage.root) 92 | 93 | assert.Equal(t, freelistPageNum, dal.freelistPage) 94 | assert.Equal(t, rootPageNum, dal.root) 95 | } 96 | 97 | func TestCreateDalWithExistingFile(t *testing.T) { 98 | // Make sure file exists 99 | _, err := os.Stat(getExpectedResultFileName(t.Name())) 100 | require.NoError(t, err) 101 | 102 | dal, cleanFunc := createTestDAL(t) 103 | defer cleanFunc() 104 | 105 | metaPage, err := dal.readMeta() 106 | require.NoError(t, err) 107 | 108 | freelistPageNum := pgnum(1) 109 | rootPageNum := pgnum(2) 110 | assert.Equal(t, freelistPageNum, metaPage.freelistPage) 111 | assert.Equal(t, rootPageNum, metaPage.root) 112 | 113 | assert.Equal(t, freelistPageNum, dal.freelistPage) 114 | assert.Equal(t, rootPageNum, dal.root) 115 | } 116 | -------------------------------------------------------------------------------- /db.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import ( 4 | "os" 5 | "sync" 6 | ) 7 | 8 | type DB struct { 9 | rwlock sync.RWMutex // Allows only one writer at a time 10 | *dal 11 | } 12 | 13 | func Open(path string, options *Options) (*DB, error) { 14 | options.pageSize = os.Getpagesize() 15 | dal, err := newDal(path, options) 16 | if err != nil { 17 | return nil, err 18 | } 19 | 20 | db := &DB{ 21 | sync.RWMutex{}, 22 | dal, 23 | } 24 | 25 | return db, nil 26 | } 27 | 28 | func (db *DB) Close() error { 29 | return db.close() 30 | } 31 | 32 | func (db *DB) ReadTx() *tx { 33 | db.rwlock.RLock() 34 | return newTx(db, false) 35 | } 36 | 37 | func (db *DB) WriteTx() *tx { 38 | db.rwlock.Lock() 39 | return newTx(db, true) 40 | } -------------------------------------------------------------------------------- /db_test.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import ( 4 | "github.com/stretchr/testify/assert" 5 | "github.com/stretchr/testify/require" 6 | "testing" 7 | ) 8 | 9 | func TestDB_CreateCollectionPutItem(t *testing.T) { 10 | db, err := Open(getTempFileName(), &Options{MinFillPercent: 0.5, MaxFillPercent: 1.0}) 11 | require.NoError(t, err) 12 | 13 | tx := db.WriteTx() 14 | collectionName := testCollectionName 15 | createdCollection, err := tx.CreateCollection(collectionName) 16 | require.NoError(t, err) 17 | 18 | newKey := []byte("0") 19 | newVal := []byte("1") 20 | err = createdCollection.Put(newKey, newVal) 21 | require.NoError(t, err) 22 | 23 | item, err := createdCollection.Find(newKey) 24 | require.NoError(t, err) 25 | 26 | assert.Equal(t, newKey, item.key) 27 | assert.Equal(t, newVal, item.value) 28 | 29 | err = tx.Commit() 30 | require.NoError(t, err) 31 | } 32 | 33 | func TestDB_WritersDontBlockReaders(t *testing.T) { 34 | t.Skip() 35 | db, err := Open(getTempFileName(), &Options{MinFillPercent: 0.5, MaxFillPercent: 1.0}) 36 | require.NoError(t, err) 37 | 38 | tx := db.WriteTx() 39 | collectionName := testCollectionName 40 | createdCollection, err := tx.CreateCollection(collectionName) 41 | require.NoError(t, err) 42 | 43 | newKey := []byte("0") 44 | newVal := []byte("1") 45 | err = createdCollection.Put(newKey, newVal) 46 | require.NoError(t, err) 47 | 48 | item, err := createdCollection.Find(newKey) 49 | require.NoError(t, err) 50 | 51 | assert.Equal(t, newKey, item.key) 52 | assert.Equal(t, newVal, item.value) 53 | 54 | err = tx.Commit() 55 | require.NoError(t, err) 56 | 57 | // Now open a write tx and try to read while that tx is open 58 | holdingTx := db.WriteTx() 59 | 60 | readTx := db.ReadTx() 61 | 62 | collection, err := readTx.GetCollection(createdCollection.name) 63 | areCollectionsEqual(t, createdCollection, collection) 64 | 65 | err = readTx.Commit() 66 | require.NoError(t, err) 67 | 68 | err = holdingTx.Commit() 69 | require.NoError(t, err) 70 | } 71 | 72 | func TestDB_ReadersDontSeeUncommittedChanges(t *testing.T) { 73 | t.Skip() 74 | db, err := Open(getTempFileName(), &Options{MinFillPercent: 0.5, MaxFillPercent: 1.0}) 75 | require.NoError(t, err) 76 | 77 | tx := db.WriteTx() 78 | collectionName := testCollectionName 79 | createdCollection, err := tx.CreateCollection(collectionName) 80 | require.NoError(t, err) 81 | 82 | err = tx.Commit() 83 | require.NoError(t, err) 84 | 85 | tx2 := db.WriteTx() 86 | createdCollection, err = tx2.GetCollection(createdCollection.name) 87 | require.NoError(t, err) 88 | 89 | newKey := createItem("0") 90 | newVal := createItem("1") 91 | err = createdCollection.Put(newKey, newVal) 92 | require.NoError(t, err) 93 | 94 | readTx := db.ReadTx() 95 | 96 | collection, err := readTx.GetCollection(createdCollection.name) 97 | areCollectionsEqual(t, createdCollection, collection) 98 | 99 | item, err := collection.Find(newKey) 100 | require.NoError(t, err) 101 | assert.Nil(t, item) 102 | 103 | err = readTx.Commit() 104 | require.NoError(t, err) 105 | 106 | err = tx2.Commit() 107 | require.NoError(t, err) 108 | } 109 | 110 | func TestDB_DeleteItem(t *testing.T) { 111 | db, err := Open(getTempFileName(), &Options{MinFillPercent: testMinPercentage, MaxFillPercent: testMaxPercentage}) 112 | require.NoError(t, err) 113 | 114 | tx := db.WriteTx() 115 | 116 | collectionName := testCollectionName 117 | createdCollection, err := tx.CreateCollection(collectionName) 118 | require.NoError(t, err) 119 | 120 | newKey := []byte("0") 121 | newVal := []byte("1") 122 | err = createdCollection.Put(newKey, newVal) 123 | require.NoError(t, err) 124 | 125 | item, err := createdCollection.Find(newKey) 126 | require.NoError(t, err) 127 | 128 | assert.Equal(t, newKey, item.key) 129 | assert.Equal(t, newVal, item.value) 130 | 131 | err = createdCollection.Remove(item.key) 132 | require.NoError(t, err) 133 | 134 | item, err = createdCollection.Find(newKey) 135 | require.NoError(t, err) 136 | 137 | assert.Nil(t, item) 138 | 139 | err = tx.Commit() 140 | require.NoError(t, err) 141 | } 142 | -------------------------------------------------------------------------------- /expected/TestCreateDalIncorrectMagicNumber: -------------------------------------------------------------------------------- 1 |  -------------------------------------------------------------------------------- /expected/TestCreateDalWithExistingFile: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/amit-davidson/LibraDB/4a154c8cb27ec9968cc9f150a39edf51cacb1b19/expected/TestCreateDalWithExistingFile -------------------------------------------------------------------------------- /expected/TestDeserializeCollection: -------------------------------------------------------------------------------- 1 |  -------------------------------------------------------------------------------- /expected/TestDeserializeWithChildNodes: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/amit-davidson/LibraDB/4a154c8cb27ec9968cc9f150a39edf51cacb1b19/expected/TestDeserializeWithChildNodes -------------------------------------------------------------------------------- /expected/TestDeserializeWithoutChildNodes: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/amit-davidson/LibraDB/4a154c8cb27ec9968cc9f150a39edf51cacb1b19/expected/TestDeserializeWithoutChildNodes -------------------------------------------------------------------------------- /expected/TestFreelistDeserialize: -------------------------------------------------------------------------------- 1 |  -------------------------------------------------------------------------------- /expected/TestFreelistSerialize: -------------------------------------------------------------------------------- 1 |  -------------------------------------------------------------------------------- /expected/TestMetaDeserialize: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/amit-davidson/LibraDB/4a154c8cb27ec9968cc9f150a39edf51cacb1b19/expected/TestMetaDeserialize -------------------------------------------------------------------------------- /expected/TestMetaSerialize: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/amit-davidson/LibraDB/4a154c8cb27ec9968cc9f150a39edf51cacb1b19/expected/TestMetaSerialize -------------------------------------------------------------------------------- /expected/TestSerializeCollection: -------------------------------------------------------------------------------- 1 |  -------------------------------------------------------------------------------- /expected/TestSerializeWithChildNodes: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/amit-davidson/LibraDB/4a154c8cb27ec9968cc9f150a39edf51cacb1b19/expected/TestSerializeWithChildNodes -------------------------------------------------------------------------------- /expected/TestSerializeWithoutChildNodes: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/amit-davidson/LibraDB/4a154c8cb27ec9968cc9f150a39edf51cacb1b19/expected/TestSerializeWithoutChildNodes -------------------------------------------------------------------------------- /freelist.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import "encoding/binary" 4 | 5 | // metaPage is the maximum pgnum that is used by the db for its own purposes. For now, only page 0 is used as the 6 | // header page. It means all other page numbers can be used. 7 | const metaPage = 0 8 | 9 | // freelist manages the manages free and used pages. 10 | type freelist struct { 11 | // maxPage holds the latest page num allocated. releasedPages holds all the ids that were released during 12 | // delete. New page ids are first given from the releasedPageIDs to avoid growing the file. If it's empty, then 13 | // maxPage is incremented and a new page is created thus increasing the file size. 14 | maxPage pgnum 15 | releasedPages []pgnum 16 | } 17 | 18 | func newFreelist() *freelist { 19 | return &freelist{ 20 | maxPage: metaPage, 21 | releasedPages: []pgnum{}, 22 | } 23 | } 24 | 25 | // getNextPage returns page ids for writing New page ids are first given from the releasedPageIDs to avoid growing 26 | // the file. If it's empty, then maxPage is incremented and a new page is created thus increasing the file size. 27 | func (fr *freelist) getNextPage() pgnum { 28 | if len(fr.releasedPages) != 0 { 29 | // Take the last element and remove it from the list 30 | pageID := fr.releasedPages[len(fr.releasedPages)-1] 31 | fr.releasedPages = fr.releasedPages[:len(fr.releasedPages)-1] 32 | return pageID 33 | } 34 | fr.maxPage += 1 35 | return fr.maxPage 36 | } 37 | 38 | func (fr *freelist) releasePage(page pgnum) { 39 | fr.releasedPages = append(fr.releasedPages, page) 40 | } 41 | 42 | func (fr *freelist) serialize(buf []byte) []byte { 43 | pos := 0 44 | 45 | binary.LittleEndian.PutUint16(buf[pos:], uint16(fr.maxPage)) 46 | pos += 2 47 | 48 | // released pages count 49 | binary.LittleEndian.PutUint16(buf[pos:], uint16(len(fr.releasedPages))) 50 | pos += 2 51 | 52 | for _, page := range fr.releasedPages { 53 | binary.LittleEndian.PutUint64(buf[pos:], uint64(page)) 54 | pos += pageNumSize 55 | 56 | } 57 | return buf 58 | } 59 | 60 | func (fr *freelist) deserialize(buf []byte) { 61 | pos := 0 62 | fr.maxPage = pgnum(binary.LittleEndian.Uint16(buf[pos:])) 63 | pos += 2 64 | 65 | // released pages count 66 | releasedPagesCount := int(binary.LittleEndian.Uint16(buf[pos:])) 67 | pos += 2 68 | 69 | for i := 0; i < releasedPagesCount; i++ { 70 | fr.releasedPages = append(fr.releasedPages, pgnum(binary.LittleEndian.Uint64(buf[pos:]))) 71 | pos += pageNumSize 72 | } 73 | } 74 | -------------------------------------------------------------------------------- /freelist_test.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import ( 4 | "github.com/stretchr/testify/assert" 5 | "github.com/stretchr/testify/require" 6 | "os" 7 | "testing" 8 | ) 9 | 10 | func TestFreelistSerialize(t *testing.T) { 11 | freelist := newFreelist() 12 | freelist.maxPage = 5 13 | freelist.releasedPages = []pgnum{1, 2, 3} 14 | actual := freelist.serialize(make([]byte, testPageSize, testPageSize)) 15 | 16 | expected, err := os.ReadFile(getExpectedResultFileName(t.Name())) 17 | require.NoError(t, err) 18 | 19 | assert.Equal(t, expected, actual) 20 | } 21 | 22 | func TestFreelistDeserialize(t *testing.T) { 23 | freelist, err := os.ReadFile(getExpectedResultFileName(t.Name())) 24 | actual := newFreelist() 25 | actual.deserialize(freelist) 26 | require.NoError(t, err) 27 | 28 | expected := newFreelist() 29 | expected.maxPage = 5 30 | expected.releasedPages = []pgnum{1, 2, 3} 31 | 32 | assert.Equal(t, expected, actual) 33 | } 34 | -------------------------------------------------------------------------------- /go.mod: -------------------------------------------------------------------------------- 1 | module github.com/amit-davidson/LibraDB 2 | 3 | go 1.17 4 | 5 | require ( 6 | github.com/google/uuid v1.3.0 7 | github.com/stretchr/testify v1.7.0 8 | ) 9 | 10 | require ( 11 | github.com/davecgh/go-spew v1.1.0 // indirect 12 | github.com/pmezard/go-difflib v1.0.0 // indirect 13 | gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect 14 | ) 15 | -------------------------------------------------------------------------------- /go.sum: -------------------------------------------------------------------------------- 1 | github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8= 2 | github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38= 3 | github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c= 4 | github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38= 5 | github.com/google/uuid v1.3.0 h1:t6JiXgmwXMjEs8VusXIJk2BXHsn+wx8BZdTaoZ5fu7I= 6 | github.com/google/uuid v1.3.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo= 7 | github.com/jcelliott/lumber v0.0.0-20160324203708-dd349441af25 h1:EFT6MH3igZK/dIVqgGbTqWVvkZ7wJ5iGN03SVtvvdd8= 8 | github.com/jcelliott/lumber v0.0.0-20160324203708-dd349441af25/go.mod h1:sWkGw/wsaHtRsT9zGQ/WyJCotGWG/Anow/9hsAcBWRw= 9 | github.com/nanobox-io/golang-scribble v0.0.0-20190309225732-aa3e7c118975 h1:zm/Rb2OsnLWCY88Njoqgo4X6yt/lx3oBNWhepX0AOMU= 10 | github.com/nanobox-io/golang-scribble v0.0.0-20190309225732-aa3e7c118975/go.mod h1:4Mct/lWCFf1jzQTTAaWtOI7sXqmG+wBeiBfT4CxoaJk= 11 | github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM= 12 | github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4= 13 | github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME= 14 | github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY= 15 | github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg= 16 | gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM= 17 | gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0= 18 | gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo= 19 | gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM= 20 | gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo= 21 | gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM= 22 | -------------------------------------------------------------------------------- /main.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | func LibraDB() { 4 | path := "libra.db" 5 | db, _ := Open(path, DefaultOptions) 6 | 7 | tx := db.WriteTx() 8 | name := []byte("test") 9 | collection, _ := tx.CreateCollection(name) 10 | 11 | key, value := []byte("key1"), []byte("value1") 12 | _ = collection.Put(key, value) 13 | 14 | _ = tx.Commit() 15 | } -------------------------------------------------------------------------------- /meta.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import "encoding/binary" 4 | 5 | const ( 6 | magicNumber uint32 = 0xD00DB00D 7 | metaPageNum = 0 8 | ) 9 | 10 | // meta is the meta page of the db 11 | type meta struct { 12 | // The database has a root collection that holds all the collections in the database. It is called root and the 13 | // root property of meta holds page number containing the root of collections collection. The keys are the 14 | // collections names and the values are the page number of the root of each collection. Then, once the collection 15 | // and the root page are located, a search inside a collection can be made. 16 | root pgnum 17 | freelistPage pgnum 18 | } 19 | 20 | func newEmptyMeta() *meta { 21 | return &meta{} 22 | } 23 | 24 | func (m *meta) serialize(buf []byte) { 25 | pos := 0 26 | binary.LittleEndian.PutUint32(buf[pos:], magicNumber) 27 | pos += magicNumberSize 28 | 29 | binary.LittleEndian.PutUint64(buf[pos:], uint64(m.root)) 30 | pos += pageNumSize 31 | 32 | binary.LittleEndian.PutUint64(buf[pos:], uint64(m.freelistPage)) 33 | pos += pageNumSize 34 | } 35 | 36 | func (m *meta) deserialize(buf []byte) { 37 | pos := 0 38 | magicNumberRes := binary.LittleEndian.Uint32(buf[pos:]) 39 | pos += magicNumberSize 40 | 41 | if magicNumberRes != magicNumber { 42 | panic("The file is not a libra db file") 43 | } 44 | 45 | m.root = pgnum(binary.LittleEndian.Uint64(buf[pos:])) 46 | pos += pageNumSize 47 | 48 | m.freelistPage = pgnum(binary.LittleEndian.Uint64(buf[pos:])) 49 | pos += pageNumSize 50 | } 51 | -------------------------------------------------------------------------------- /meta_test.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import ( 4 | "github.com/stretchr/testify/assert" 5 | "github.com/stretchr/testify/require" 6 | "os" 7 | "testing" 8 | ) 9 | 10 | func TestMetaSerialize(t *testing.T) { 11 | meta := newEmptyMeta() 12 | meta.root = 3 13 | meta.freelistPage = 4 14 | actual := make([]byte, testPageSize, testPageSize) 15 | meta.serialize(actual) 16 | 17 | expected, err := os.ReadFile(getExpectedResultFileName(t.Name())) 18 | require.NoError(t, err) 19 | 20 | assert.Equal(t, expected, actual) 21 | } 22 | 23 | func TestCreateDalIncorrectMagicNumber(t *testing.T) { 24 | actualMetaBytes, err := os.ReadFile(getExpectedResultFileName(t.Name())) 25 | require.NoError(t, err) 26 | actualMeta := newEmptyMeta() 27 | assert.Panics(t, func() { 28 | actualMeta.deserialize(actualMetaBytes) 29 | }) 30 | } 31 | 32 | func TestMetaDeserialize(t *testing.T) { 33 | actualMetaBytes, err := os.ReadFile(getExpectedResultFileName(t.Name())) 34 | actualMeta := newEmptyMeta() 35 | actualMeta.deserialize(actualMetaBytes) 36 | require.NoError(t, err) 37 | 38 | expectedMeta := newEmptyMeta() 39 | expectedMeta.root = 3 40 | expectedMeta.freelistPage = 4 41 | 42 | assert.Equal(t, expectedMeta, actualMeta) 43 | } -------------------------------------------------------------------------------- /node.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import ( 4 | "bytes" 5 | "encoding/binary" 6 | ) 7 | 8 | type Item struct { 9 | key []byte 10 | value []byte 11 | } 12 | 13 | type Node struct { 14 | // associated transaction 15 | tx *tx 16 | 17 | pageNum pgnum 18 | items []*Item 19 | childNodes []pgnum 20 | } 21 | 22 | func NewEmptyNode() *Node { 23 | return &Node{} 24 | } 25 | 26 | // NewNodeForSerialization creates a new node only with the properties that are relevant when saving to the disk 27 | func NewNodeForSerialization(items []*Item, childNodes []pgnum) *Node { 28 | return &Node{ 29 | items: items, 30 | childNodes: childNodes, 31 | } 32 | } 33 | 34 | func newItem(key []byte, value []byte) *Item { 35 | return &Item{ 36 | key: key, 37 | value: value, 38 | } 39 | } 40 | 41 | func isLast(index int, parentNode *Node) bool { 42 | return index == len(parentNode.items) 43 | } 44 | 45 | func isFirst(index int) bool { 46 | return index == 0 47 | } 48 | 49 | func (n *Node) isLeaf() bool { 50 | return len(n.childNodes) == 0 51 | } 52 | 53 | func (n *Node) writeNode(node *Node) *Node { 54 | return n.tx.writeNode(node) 55 | } 56 | 57 | func (n *Node) writeNodes(nodes ...*Node) { 58 | for _, node := range nodes { 59 | n.writeNode(node) 60 | } 61 | } 62 | 63 | func (n *Node) getNode(pageNum pgnum) (*Node, error) { 64 | return n.tx.getNode(pageNum) 65 | } 66 | 67 | // isOverPopulated checks if the node size is bigger than the size of a page. 68 | func (n *Node) isOverPopulated() bool { 69 | return n.tx.db.isOverPopulated(n) 70 | } 71 | 72 | // canSpareAnElement checks if the node size is big enough to populate a page after giving away one item. 73 | func (n *Node) canSpareAnElement() bool { 74 | splitIndex := n.tx.db.getSplitIndex(n) 75 | if splitIndex == -1 { 76 | return false 77 | } 78 | return true 79 | } 80 | 81 | // isUnderPopulated checks if the node size is smaller than the size of a page. 82 | func (n *Node) isUnderPopulated() bool { 83 | return n.tx.db.isUnderPopulated(n) 84 | } 85 | 86 | func (n *Node) serialize(buf []byte) []byte { 87 | leftPos := 0 88 | rightPos := len(buf) - 1 89 | 90 | // Add page header: isLeaf, key-value pairs count, node num 91 | // isLeaf 92 | isLeaf := n.isLeaf() 93 | var bitSetVar uint64 94 | if isLeaf { 95 | bitSetVar = 1 96 | } 97 | buf[leftPos] = byte(bitSetVar) 98 | leftPos += 1 99 | 100 | // key-value pairs count 101 | binary.LittleEndian.PutUint16(buf[leftPos:], uint16(len(n.items))) 102 | leftPos += 2 103 | 104 | // We use slotted pages for storing data in the page. It means the actual keys and values (the cells) are appended 105 | // to right of the page whereas offsets have a fixed size and are appended from the left. 106 | // It's easier to preserve the logical order (alphabetical in the case of b-tree) using the metadata and performing 107 | // pointer arithmetic. Using the data itself is harder as it varies by size. 108 | 109 | // Page structure is: 110 | // ---------------------------------------------------------------------------------- 111 | // | Page | key-value / child node key-value | key-value | 112 | // | Header | offset / pointer offset .... | data ..... | 113 | // ---------------------------------------------------------------------------------- 114 | 115 | for i := 0; i < len(n.items); i++ { 116 | item := n.items[i] 117 | if !isLeaf { 118 | childNode := n.childNodes[i] 119 | 120 | // Write the child page as a fixed size of 8 bytes 121 | binary.LittleEndian.PutUint64(buf[leftPos:], uint64(childNode)) 122 | leftPos += pageNumSize 123 | } 124 | 125 | klen := len(item.key) 126 | vlen := len(item.value) 127 | 128 | // write offset 129 | offset := rightPos - klen - vlen - 2 130 | binary.LittleEndian.PutUint16(buf[leftPos:], uint16(offset)) 131 | leftPos += 2 132 | 133 | rightPos -= vlen 134 | copy(buf[rightPos:], item.value) 135 | 136 | rightPos -= 1 137 | buf[rightPos] = byte(vlen) 138 | 139 | rightPos -= klen 140 | copy(buf[rightPos:], item.key) 141 | 142 | rightPos -= 1 143 | buf[rightPos] = byte(klen) 144 | } 145 | 146 | if !isLeaf { 147 | // Write the last child node 148 | lastChildNode := n.childNodes[len(n.childNodes)-1] 149 | // Write the child page as a fixed size of 8 bytes 150 | binary.LittleEndian.PutUint64(buf[leftPos:], uint64(lastChildNode)) 151 | } 152 | 153 | return buf 154 | } 155 | 156 | func (n *Node) deserialize(buf []byte) { 157 | leftPos := 0 158 | 159 | // Read header 160 | isLeaf := uint16(buf[0]) 161 | 162 | itemsCount := int(binary.LittleEndian.Uint16(buf[1:3])) 163 | leftPos += 3 164 | 165 | // Read body 166 | for i := 0; i < itemsCount; i++ { 167 | if isLeaf == 0 { // False 168 | pageNum := binary.LittleEndian.Uint64(buf[leftPos:]) 169 | leftPos += pageNumSize 170 | 171 | n.childNodes = append(n.childNodes, pgnum(pageNum)) 172 | } 173 | 174 | // Read offset 175 | offset := binary.LittleEndian.Uint16(buf[leftPos:]) 176 | leftPos += 2 177 | 178 | klen := uint16(buf[int(offset)]) 179 | offset += 1 180 | 181 | key := buf[offset : offset+klen] 182 | offset += klen 183 | 184 | vlen := uint16(buf[int(offset)]) 185 | offset += 1 186 | 187 | value := buf[offset : offset+vlen] 188 | offset += vlen 189 | n.items = append(n.items, newItem(key, value)) 190 | } 191 | 192 | if isLeaf == 0 { // False 193 | // Read the last child node 194 | pageNum := pgnum(binary.LittleEndian.Uint64(buf[leftPos:])) 195 | n.childNodes = append(n.childNodes, pageNum) 196 | } 197 | } 198 | 199 | // elementSize returns the size of a key-value-childNode triplet at a given index. If the node is a leaf, then the size 200 | // of a key-value pair is returned. It's assumed i <= len(n.items) 201 | func (n *Node) elementSize(i int) int { 202 | size := 0 203 | size += len(n.items[i].key) 204 | size += len(n.items[i].value) 205 | size += pageNumSize // 8 is the pgnum size 206 | return size 207 | } 208 | 209 | // nodeSize returns the node's size in bytes 210 | func (n *Node) nodeSize() int { 211 | size := 0 212 | size += nodeHeaderSize 213 | 214 | for i := range n.items { 215 | size += n.elementSize(i) 216 | } 217 | 218 | // Add last page 219 | size += pageNumSize // 8 is the pgnum size 220 | return size 221 | } 222 | 223 | // findKey searches for a key inside the tree. Once the key is found, the parent node and the correct index are returned 224 | // so the key itself can be accessed in the following way parent[index]. A list of the node ancestors (not including the 225 | // node itself) is also returned. 226 | // If the key isn't found, we have 2 options. If exact is true, it means we expect findKey 227 | // to find the key, so a falsey answer. If exact is false, then findKey is used to locate where a new key should be 228 | // inserted so the position is returned. 229 | func (n *Node) findKey(key []byte, exact bool) (int, *Node, []int ,error) { 230 | ancestorsIndexes := []int{0} // index of root 231 | index, node, err := findKeyHelper(n, key, exact, &ancestorsIndexes) 232 | if err != nil { 233 | return -1, nil, nil, err 234 | } 235 | return index, node, ancestorsIndexes, nil 236 | } 237 | 238 | func findKeyHelper(node *Node, key []byte, exact bool, ancestorsIndexes *[]int) (int, *Node ,error) { 239 | wasFound, index := node.findKeyInNode(key) 240 | if wasFound { 241 | return index, node, nil 242 | } 243 | 244 | if node.isLeaf() { 245 | if exact { 246 | return -1, nil, nil 247 | } 248 | return index, node, nil 249 | } 250 | 251 | *ancestorsIndexes = append(*ancestorsIndexes, index) 252 | nextChild, err := node.getNode(node.childNodes[index]) 253 | if err != nil { 254 | return -1, nil, err 255 | } 256 | return findKeyHelper(nextChild, key, exact, ancestorsIndexes) 257 | } 258 | 259 | // findKeyInNode iterates all the items and finds the key. If the key is found, then the item is returned. If the key 260 | // isn't found then return the index where it should have been (the first index that key is greater than it's previous) 261 | func (n *Node) findKeyInNode(key []byte) (bool, int) { 262 | for i, existingItem := range n.items { 263 | res := bytes.Compare(existingItem.key, key) 264 | if res == 0 { // Keys match 265 | return true, i 266 | } 267 | 268 | // The key is bigger than the previous item, so it doesn't exist in the node, but may exist in child nodes. 269 | if res == 1 { 270 | return false, i 271 | } 272 | } 273 | 274 | // The key isn't bigger than any of the items which means it's in the last index. 275 | return false, len(n.items) 276 | } 277 | 278 | func (n *Node) addItem(item *Item, insertionIndex int) int { 279 | if len(n.items) == insertionIndex { // nil or empty slice or after last element 280 | n.items = append(n.items, item) 281 | return insertionIndex 282 | } 283 | 284 | n.items = append(n.items[:insertionIndex+1], n.items[insertionIndex:]...) 285 | n.items[insertionIndex] = item 286 | return insertionIndex 287 | } 288 | 289 | // split rebalances the tree after adding. After insertion the modified node has to be checked to make sure it 290 | // didn't exceed the maximum number of elements. If it did, then it has to be split and rebalanced. The transformation 291 | // is depicted in the graph below. If it's not a leaf node, then the children has to be moved as well as shown. 292 | // This may leave the parent unbalanced by having too many items so rebalancing has to be checked for all the ancestors. 293 | // The split is performed in a for loop to support splitting a node more than once. (Though in practice used only once). 294 | // n n 295 | // 3 3,6 296 | // / \ ------> / | \ 297 | // a modifiedNode a modifiedNode newNode 298 | // 1,2 4,5,6,7,8 1,2 4,5 7,8 299 | func (n *Node) split(nodeToSplit *Node, nodeToSplitIndex int) { 300 | // The first index where min amount of bytes to populate a page is achieved. Then add 1 so it will be split one 301 | // index after. 302 | splitIndex := nodeToSplit.tx.db.getSplitIndex(nodeToSplit) 303 | 304 | middleItem := nodeToSplit.items[splitIndex] 305 | var newNode *Node 306 | 307 | if nodeToSplit.isLeaf() { 308 | newNode = n.writeNode(n.tx.newNode(nodeToSplit.items[splitIndex+1:], []pgnum{})) 309 | nodeToSplit.items = nodeToSplit.items[:splitIndex] 310 | } else { 311 | newNode = n.writeNode(n.tx.newNode(nodeToSplit.items[splitIndex+1:], nodeToSplit.childNodes[splitIndex+1:])) 312 | nodeToSplit.items = nodeToSplit.items[:splitIndex] 313 | nodeToSplit.childNodes = nodeToSplit.childNodes[:splitIndex+1] 314 | } 315 | n.addItem(middleItem, nodeToSplitIndex) 316 | if len(n.childNodes) == nodeToSplitIndex+1 { // If middle of list, then move items forward 317 | n.childNodes = append(n.childNodes, newNode.pageNum) 318 | } else { 319 | n.childNodes = append(n.childNodes[:nodeToSplitIndex+1], n.childNodes[nodeToSplitIndex:]...) 320 | n.childNodes[nodeToSplitIndex+1] = newNode.pageNum 321 | } 322 | 323 | n.writeNodes(n, nodeToSplit) 324 | } 325 | 326 | // rebalanceRemove rebalances the tree after a remove operation. This can be either by rotating to the right, to the 327 | // left or by merging. First, the sibling nodes are checked to see if they have enough items for rebalancing 328 | // (>= minItems+1). If they don't have enough items, then merging with one of the sibling nodes occurs. This may leave 329 | // the parent unbalanced by having too little items so rebalancing has to be checked for all the ancestors. 330 | func (n *Node) rebalanceRemove(unbalancedNode *Node, unbalancedNodeIndex int) error { 331 | pNode := n 332 | 333 | // Right rotate 334 | if unbalancedNodeIndex != 0 { 335 | leftNode, err := n.getNode(pNode.childNodes[unbalancedNodeIndex-1]) 336 | if err != nil { 337 | return err 338 | } 339 | if leftNode.canSpareAnElement() { 340 | rotateRight(leftNode, pNode, unbalancedNode, unbalancedNodeIndex) 341 | n.writeNodes(leftNode, pNode, unbalancedNode) 342 | return nil 343 | } 344 | } 345 | 346 | // Left Balance 347 | if unbalancedNodeIndex != len(pNode.childNodes)-1 { 348 | rightNode, err := n.getNode(pNode.childNodes[unbalancedNodeIndex+1]) 349 | if err != nil { 350 | return err 351 | } 352 | if rightNode.canSpareAnElement() { 353 | rotateLeft(unbalancedNode, pNode, rightNode, unbalancedNodeIndex) 354 | n.writeNodes(unbalancedNode, pNode, rightNode) 355 | return nil 356 | } 357 | } 358 | 359 | // The merge function merges a given node with its node to the right. So by default, we merge an unbalanced node 360 | // with its right sibling. In the case where the unbalanced node is the leftmost, we have to replace the merge 361 | // parameters, so the unbalanced node right sibling, will be merged into the unbalanced node. 362 | if unbalancedNodeIndex == 0 { 363 | rightNode, err := n.getNode(n.childNodes[unbalancedNodeIndex+1]) 364 | if err != nil { 365 | return err 366 | } 367 | 368 | return pNode.merge(rightNode, unbalancedNodeIndex+1) 369 | } 370 | 371 | return pNode.merge(unbalancedNode, unbalancedNodeIndex) 372 | } 373 | 374 | // removeItemFromLeaf removes an item from a leaf node. It means there is no handling of child nodes. 375 | func (n *Node) removeItemFromLeaf(index int) { 376 | n.items = append(n.items[:index], n.items[index+1:]...) 377 | n.writeNode(n) 378 | } 379 | 380 | func (n *Node) removeItemFromInternal(index int) ([]int, error) { 381 | // Take element before inorder (The biggest element from the left branch), put it in the removed index and remove 382 | // it from the original node. Track in affectedNodes any nodes in the path leading to that node. It will be used 383 | // in case the tree needs to be rebalanced. 384 | // p 385 | // / 386 | // .. 387 | // / \ 388 | // .. a 389 | 390 | affectedNodes := make([]int, 0) 391 | affectedNodes = append(affectedNodes, index) 392 | 393 | // Starting from its left child, descend to the rightmost descendant. 394 | aNode, err := n.getNode(n.childNodes[index]) 395 | if err != nil { 396 | return nil, err 397 | } 398 | 399 | for !aNode.isLeaf() { 400 | traversingIndex := len(n.childNodes) - 1 401 | aNode, err = aNode.getNode(aNode.childNodes[traversingIndex]) 402 | if err != nil { 403 | return nil, err 404 | } 405 | affectedNodes = append(affectedNodes, traversingIndex) 406 | } 407 | 408 | // Replace the item that should be removed with the item before inorder which we just found. 409 | n.items[index] = aNode.items[len(aNode.items)-1] 410 | aNode.items = aNode.items[:len(aNode.items)-1] 411 | n.writeNodes(n, aNode) 412 | 413 | return affectedNodes, nil 414 | } 415 | 416 | func rotateRight(aNode, pNode, bNode *Node, bNodeIndex int) { 417 | // p p 418 | // 4 3 419 | // / \ ------> / \ 420 | // a b (unbalanced) a b (unbalanced) 421 | // 1,2,3 5 1,2 4,5 422 | 423 | // Get last item and remove it 424 | aNodeItem := aNode.items[len(aNode.items)-1] 425 | aNode.items = aNode.items[:len(aNode.items)-1] 426 | 427 | // Get item from parent node and assign the aNodeItem item instead 428 | pNodeItemIndex := bNodeIndex - 1 429 | if isFirst(bNodeIndex) { 430 | pNodeItemIndex = 0 431 | } 432 | pNodeItem := pNode.items[pNodeItemIndex] 433 | pNode.items[pNodeItemIndex] = aNodeItem 434 | 435 | // Assign parent item to b and make it first 436 | bNode.items = append([]*Item{pNodeItem}, bNode.items...) 437 | 438 | // If it's an inner leaf then move children as well. 439 | if !aNode.isLeaf() { 440 | childNodeToShift := aNode.childNodes[len(aNode.childNodes)-1] 441 | aNode.childNodes = aNode.childNodes[:len(aNode.childNodes)-1] 442 | bNode.childNodes = append([]pgnum{childNodeToShift}, bNode.childNodes...) 443 | } 444 | } 445 | 446 | func rotateLeft(aNode, pNode, bNode *Node, bNodeIndex int) { 447 | // p p 448 | // 2 3 449 | // / \ ------> / \ 450 | // a(unbalanced) b a(unbalanced) b 451 | // 1 3,4,5 1,2 4,5 452 | 453 | // Get first item and remove it 454 | bNodeItem := bNode.items[0] 455 | bNode.items = bNode.items[1:] 456 | 457 | // Get item from parent node and assign the bNodeItem item instead 458 | pNodeItemIndex := bNodeIndex 459 | if isLast(bNodeIndex, pNode) { 460 | pNodeItemIndex = len(pNode.items) - 1 461 | } 462 | pNodeItem := pNode.items[pNodeItemIndex] 463 | pNode.items[pNodeItemIndex] = bNodeItem 464 | 465 | // Assign parent item to a and make it last 466 | aNode.items = append(aNode.items, pNodeItem) 467 | 468 | // If it's an inner leaf then move children as well. 469 | if !bNode.isLeaf() { 470 | childNodeToShift := bNode.childNodes[0] 471 | bNode.childNodes = bNode.childNodes[1:] 472 | aNode.childNodes = append(aNode.childNodes, childNodeToShift) 473 | } 474 | } 475 | 476 | func (n *Node) merge(bNode *Node, bNodeIndex int) error { 477 | // p p 478 | // 3,5 5 479 | // / | \ ------> / \ 480 | // a b c a c 481 | // 1,2 4 6,7 1,2,3,4 6,7 482 | aNode, err := n.getNode(n.childNodes[bNodeIndex-1]) 483 | if err != nil { 484 | return err 485 | } 486 | 487 | // Take the item from the parent, remove it and add it to the unbalanced node 488 | pNodeItem := n.items[bNodeIndex-1] 489 | n.items = append(n.items[:bNodeIndex-1], n.items[bNodeIndex:]...) 490 | aNode.items = append(aNode.items, pNodeItem) 491 | 492 | aNode.items = append(aNode.items, bNode.items...) 493 | n.childNodes = append(n.childNodes[:bNodeIndex], n.childNodes[bNodeIndex+1:]...) 494 | if !aNode.isLeaf() { 495 | aNode.childNodes = append(aNode.childNodes, bNode.childNodes...) 496 | } 497 | n.writeNodes(aNode, n) 498 | n.tx.deleteNode(bNode) 499 | return nil 500 | } -------------------------------------------------------------------------------- /node_test.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import ( 4 | "bytes" 5 | "github.com/stretchr/testify/assert" 6 | "github.com/stretchr/testify/require" 7 | "os" 8 | "strconv" 9 | "testing" 10 | ) 11 | 12 | func Test_AddSingle(t *testing.T) { 13 | db, cleanFunc := createTestDB(t) 14 | defer cleanFunc() 15 | 16 | tx := db.WriteTx() 17 | collection, err := tx.CreateCollection(testCollectionName) 18 | require.NoError(t, err) 19 | 20 | value := createItem("0") 21 | err = collection.Put(value, value) 22 | require.NoError(t, err) 23 | 24 | err = tx.Commit() 25 | require.NoError(t, err) 26 | 27 | expectedDB, expectedCleanFunc := createTestDB(t) 28 | defer expectedCleanFunc() 29 | 30 | expectedTx := expectedDB.WriteTx() 31 | 32 | expectedRoot := expectedTx.writeNode(expectedTx.newNode(createItems("0"), []pgnum{})) 33 | expectedCollection, err := expectedTx.createCollection(newCollection(testCollectionName, expectedRoot.pageNum)) 34 | require.NoError(t, err) 35 | 36 | err = expectedTx.Commit() 37 | require.NoError(t, err) 38 | 39 | areTreesEqual(t, expectedCollection, collection) 40 | } 41 | 42 | func Test_RemoveFromRootSingleElement(t *testing.T) { 43 | db, cleanFunc := createTestDB(t) 44 | defer cleanFunc() 45 | 46 | tx := db.WriteTx() 47 | collection, err := tx.CreateCollection(testCollectionName) 48 | require.NoError(t, err) 49 | 50 | value := createItem("0") 51 | err = collection.Put(value, value) 52 | require.NoError(t, err) 53 | 54 | err = collection.Remove(value) 55 | require.NoError(t, err) 56 | 57 | err = tx.Commit() 58 | require.NoError(t, err) 59 | 60 | expectedDBAfterRemoval, cleanFuncAfterRemoval := createTestDB(t) 61 | defer cleanFuncAfterRemoval() 62 | 63 | expectedTxAfterRemoval := expectedDBAfterRemoval.WriteTx() 64 | 65 | expectedRootAfterRemoval := expectedTxAfterRemoval.writeNode(expectedTxAfterRemoval.newNode([]*Item{}, []pgnum{})) 66 | 67 | expectedCollectionAfterRemoval, err := expectedTxAfterRemoval.createCollection(newCollection(testCollectionName, expectedRootAfterRemoval.pageNum)) 68 | 69 | err = expectedTxAfterRemoval.Commit() 70 | require.NoError(t, err) 71 | 72 | areTreesEqual(t, expectedCollectionAfterRemoval, collection) 73 | } 74 | 75 | func Test_AddMultiple(t *testing.T) { 76 | db, cleanFunc := createTestDB(t) 77 | defer cleanFunc() 78 | 79 | tx := db.WriteTx() 80 | collection, err := tx.CreateCollection(testCollectionName) 81 | require.NoError(t, err) 82 | 83 | numOfElements := mockNumberOfElements 84 | for i := 0; i < numOfElements; i++ { 85 | val := createItem(strconv.Itoa(i)) 86 | err = collection.Put(val, val) 87 | require.NoError(t, err) 88 | } 89 | err = tx.Commit() 90 | require.NoError(t, err) 91 | 92 | // Tree is balanced 93 | expected, expectedCleanFunc := createTestMockTree(t) 94 | defer expectedCleanFunc() 95 | areTreesEqual(t, expected, collection) 96 | } 97 | 98 | func Test_AddAndRebalanceSplit(t *testing.T) { 99 | db, cleanFunc := createTestDB(t) 100 | defer cleanFunc() 101 | 102 | tx := db.WriteTx() 103 | child0 := tx.writeNode(tx.newNode(createItems("0", "1", "2", "3"), []pgnum{})) 104 | 105 | child1 := tx.writeNode(tx.newNode(createItems("5", "6", "7", "8"), []pgnum{})) 106 | 107 | root := tx.writeNode(tx.newNode(createItems("4"), []pgnum{child0.pageNum, child1.pageNum})) 108 | 109 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 110 | require.NoError(t, err) 111 | 112 | val := createItem("9") 113 | err = collection.Put(val, val) 114 | require.NoError(t, err) 115 | 116 | err = tx.Commit() 117 | require.NoError(t, err) 118 | 119 | expectedTestDB, expectedCleanFunc := createTestDB(t) 120 | defer expectedCleanFunc() 121 | 122 | testTx := expectedTestDB.WriteTx() 123 | 124 | expectedChild0 := testTx.writeNode(testTx.newNode(createItems("0", "1", "2", "3"), []pgnum{})) 125 | 126 | expectedChild1 := testTx.writeNode(testTx.newNode(createItems("5", "6"), []pgnum{})) 127 | 128 | expectedChild2 := testTx.writeNode(testTx.newNode(createItems("8", "9"), []pgnum{})) 129 | 130 | expectedRoot := testTx.writeNode(testTx.newNode(createItems("4", "7"), []pgnum{expectedChild0.pageNum, expectedChild1.pageNum, expectedChild2.pageNum})) 131 | 132 | expectedCollection, err := testTx.createCollection(newCollection(testCollectionName, expectedRoot.pageNum)) 133 | require.NoError(t, err) 134 | 135 | err = testTx.Commit() 136 | require.NoError(t, err) 137 | 138 | // Tree is balanced 139 | areTreesEqual(t, expectedCollection, collection) 140 | } 141 | 142 | func Test_SplitAndMerge(t *testing.T) { 143 | db, cleanFunc := createTestDB(t) 144 | defer cleanFunc() 145 | 146 | tx := db.WriteTx() 147 | child0 := tx.writeNode(tx.newNode(createItems("0", "1", "2", "3"), []pgnum{})) 148 | 149 | child1 := tx.writeNode(tx.newNode(createItems("5", "6", "7", "8"), []pgnum{})) 150 | 151 | root := tx.writeNode(tx.newNode(createItems("4"), []pgnum{child0.pageNum, child1.pageNum})) 152 | 153 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 154 | require.NoError(t, err) 155 | 156 | val := createItem("9") 157 | err = collection.Put(val, val) 158 | require.NoError(t, err) 159 | 160 | err = tx.Commit() 161 | require.NoError(t, err) 162 | 163 | expectedTestDB, expectedCleanFunc := createTestDB(t) 164 | defer expectedCleanFunc() 165 | 166 | testTx := expectedTestDB.WriteTx() 167 | 168 | expectedChild0 := testTx.writeNode(testTx.newNode(createItems("0", "1", "2", "3"), []pgnum{})) 169 | 170 | expectedChild1 := testTx.writeNode(testTx.newNode(createItems("5", "6"), []pgnum{})) 171 | 172 | expectedChild2 := testTx.writeNode(testTx.newNode(createItems("8", "9"), []pgnum{})) 173 | 174 | expectedRoot := testTx.writeNode(testTx.newNode(createItems("4", "7"), []pgnum{expectedChild0.pageNum, expectedChild1.pageNum, expectedChild2.pageNum})) 175 | 176 | expectedCollection, err := testTx.createCollection(newCollection(testCollectionName, expectedRoot.pageNum)) 177 | require.NoError(t, err) 178 | 179 | // Tree is balanced 180 | areTreesEqual(t, expectedCollection, collection) 181 | 182 | err = testTx.Commit() 183 | require.NoError(t, err) 184 | 185 | removeTx := db.WriteTx() 186 | collection , err = removeTx.GetCollection(collection.name) 187 | require.NoError(t, err) 188 | 189 | err = collection.Remove(val) 190 | require.NoError(t, err) 191 | 192 | err = removeTx.Commit() 193 | require.NoError(t, err) 194 | 195 | expectedDBAfterRemoval, expectedDBCleanFunc := createTestDB(t) 196 | defer expectedDBCleanFunc() 197 | 198 | expectedTxAfterRemoval := expectedDBAfterRemoval.WriteTx() 199 | expectedChild0AfterRemoval := expectedTxAfterRemoval.writeNode(expectedTxAfterRemoval.newNode(createItems("0", "1", "2", "3"), []pgnum{})) 200 | 201 | expectedChild1AfterRemoval := expectedTxAfterRemoval.writeNode(expectedTxAfterRemoval.newNode(createItems("5", "6", "7", "8"), []pgnum{})) 202 | 203 | expectedRootAfterRemoval := expectedTxAfterRemoval.writeNode(expectedTxAfterRemoval.newNode(createItems("4"), []pgnum{expectedChild0AfterRemoval.pageNum, expectedChild1AfterRemoval.pageNum})) 204 | 205 | expectedCollectionAfterRemoval, err := expectedTxAfterRemoval.createCollection(newCollection(testCollectionName, expectedRootAfterRemoval.pageNum)) 206 | require.NoError(t, err) 207 | 208 | err = expectedTxAfterRemoval.Commit() 209 | require.NoError(t, err) 210 | 211 | areTreesEqual(t, expectedCollectionAfterRemoval, collection) 212 | } 213 | 214 | func Test_RemoveFromRootWithoutRebalance(t *testing.T) { 215 | db, cleanFunc := createTestDB(t) 216 | defer cleanFunc() 217 | 218 | tx := db.WriteTx() 219 | collection, err := tx.CreateCollection(testCollectionName) 220 | require.NoError(t, err) 221 | 222 | numOfElements := mockNumberOfElements 223 | for i := 0; i < numOfElements; i++ { 224 | val := createItem(strconv.Itoa(i)) 225 | err = collection.Put(val, val) 226 | require.NoError(t, err) 227 | } 228 | 229 | // Remove an element 230 | err = collection.Remove(createItem("7")) 231 | require.NoError(t, err) 232 | 233 | err = tx.Commit() 234 | require.NoError(t, err) 235 | 236 | expectedDB, expectedCleanFunc := createTestDB(t) 237 | defer expectedCleanFunc() 238 | 239 | expectedTestTx := expectedDB.WriteTx() 240 | 241 | expectedChild0 := expectedTestTx.writeNode(expectedTestTx.newNode(createItems("0", "1"), []pgnum{})) 242 | 243 | expectedChild1 := expectedTestTx.writeNode(expectedTestTx.newNode(createItems("3", "4"), []pgnum{})) 244 | 245 | expectedChild2 := expectedTestTx.writeNode(expectedTestTx.newNode(createItems("6", "8", "9"), []pgnum{})) 246 | 247 | expectedRoot := expectedTestTx.writeNode(expectedTestTx.newNode(createItems("2", "5"), []pgnum{expectedChild0.pageNum, expectedChild1.pageNum, expectedChild2.pageNum})) 248 | 249 | expectedCollectionAfterRemoval, err := expectedTestTx.createCollection(newCollection(testCollectionName, expectedRoot.pageNum)) 250 | require.NoError(t, err) 251 | 252 | err = expectedTestTx.Commit() 253 | require.NoError(t, err) 254 | 255 | areTreesEqual(t, expectedCollectionAfterRemoval, collection) 256 | } 257 | 258 | func Test_RemoveFromRootAndRotateLeft(t *testing.T) { 259 | db, cleanFunc := createTestDB(t) 260 | defer cleanFunc() 261 | 262 | tx := db.WriteTx() 263 | 264 | child0 := tx.writeNode(tx.newNode(createItems("0", "1"), []pgnum{})) 265 | 266 | child1 := tx.writeNode(tx.newNode(createItems("3", "4"), []pgnum{})) 267 | 268 | child2 := tx.writeNode(tx.newNode(createItems("6", "7", "8"), []pgnum{})) 269 | 270 | root := tx.writeNode(tx.newNode(createItems("2", "5"), []pgnum{child0.pageNum, child1.pageNum, child2.pageNum})) 271 | 272 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 273 | require.NoError(t, err) 274 | 275 | // Remove an element 276 | err = collection.Remove(createItem("5")) 277 | require.NoError(t, err) 278 | 279 | err = tx.Commit() 280 | require.NoError(t, err) 281 | 282 | expectedDB, expectedCleanFunc := createTestDB(t) 283 | defer expectedCleanFunc() 284 | 285 | expectedTx := expectedDB.WriteTx() 286 | 287 | expectedChild0 := expectedTx.writeNode(expectedTx.newNode(createItems("0", "1"), []pgnum{})) 288 | 289 | expectedChild1 := expectedTx.writeNode(expectedTx.newNode(createItems("3", "4"), []pgnum{})) 290 | 291 | expectedChild2 := expectedTx.writeNode(expectedTx.newNode(createItems("7", "8"), []pgnum{})) 292 | 293 | expectedRoot := expectedTx.writeNode(expectedTx.newNode(createItems("2", "6"), []pgnum{expectedChild0.pageNum, expectedChild1.pageNum, expectedChild2.pageNum})) 294 | 295 | expectedCollection, err := expectedTx.createCollection(newCollection(testCollectionName, expectedRoot.pageNum)) 296 | require.NoError(t, err) 297 | 298 | err = expectedTx.Commit() 299 | require.NoError(t, err) 300 | 301 | areTreesEqual(t, expectedCollection, collection) 302 | } 303 | 304 | func Test_RemoveFromRootAndRotateRight(t *testing.T) { 305 | db, cleanFunc := createTestDB(t) 306 | defer cleanFunc() 307 | 308 | tx := db.WriteTx() 309 | 310 | child0 := tx.writeNode(tx.newNode(createItems("0", "1", "2"), []pgnum{})) 311 | 312 | child1 := tx.writeNode(tx.newNode(createItems("4", "5"), []pgnum{})) 313 | 314 | child2 := tx.writeNode(tx.newNode(createItems("7", "8"), []pgnum{})) 315 | 316 | root := tx.writeNode(tx.newNode(createItems("3", "6"), []pgnum{child0.pageNum, child1.pageNum, child2.pageNum})) 317 | 318 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 319 | require.NoError(t, err) 320 | 321 | // Remove an element 322 | err = collection.Remove(createItem("6")) 323 | require.NoError(t, err) 324 | 325 | err = tx.Commit() 326 | require.NoError(t, err) 327 | 328 | expectedDB, expectedCleanFunc := createTestDB(t) 329 | defer expectedCleanFunc() 330 | 331 | expectedTx := expectedDB.WriteTx() 332 | 333 | expectedChild0 := expectedTx.writeNode(expectedTx.newNode(createItems("0", "1"), []pgnum{})) 334 | 335 | expectedChild1 := expectedTx.writeNode(expectedTx.newNode(createItems("3", "4"), []pgnum{})) 336 | 337 | expectedChild2 := expectedTx.writeNode(expectedTx.newNode(createItems("7", "8"), []pgnum{})) 338 | 339 | expectedRoot := expectedTx.writeNode(expectedTx.newNode(createItems("2", "5"), []pgnum{expectedChild0.pageNum, expectedChild1.pageNum, expectedChild2.pageNum})) 340 | 341 | expectedCollection, err := expectedTx.createCollection(newCollection(testCollectionName, expectedRoot.pageNum)) 342 | require.NoError(t, err) 343 | 344 | err = expectedTx.Commit() 345 | require.NoError(t, err) 346 | 347 | areTreesEqual(t, expectedCollection, collection) 348 | } 349 | 350 | // Test_RemoveFromRootAndRebalanceMergeToUnbalanced tests when the unbalanced node is the most left one so the 351 | // merge has to happen from the right node into the unbalanced node 352 | func Test_RemoveFromRootAndRebalanceMergeToUnbalanced(t *testing.T) { 353 | db, cleanFunc := createTestDB(t) 354 | defer cleanFunc() 355 | 356 | tx := db.WriteTx() 357 | 358 | child0 := tx.writeNode(tx.newNode(createItems("0", "1"), []pgnum{})) 359 | 360 | child1 := tx.writeNode(tx.newNode(createItems("3", "4"), []pgnum{})) 361 | 362 | child2 := tx.writeNode(tx.newNode(createItems("6", "7"), []pgnum{})) 363 | 364 | root := tx.writeNode(tx.newNode(createItems("2", "5"), []pgnum{child0.pageNum, child1.pageNum, child2.pageNum})) 365 | 366 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 367 | require.NoError(t, err) 368 | 369 | // Remove an element 370 | err = collection.Remove(createItem("2")) 371 | require.NoError(t, err) 372 | 373 | err = tx.Commit() 374 | require.NoError(t, err) 375 | 376 | expectedDB, expectedCleanFunc := createTestDB(t) 377 | defer expectedCleanFunc() 378 | 379 | expectedTx := expectedDB.WriteTx() 380 | 381 | expectedChild0 := expectedTx.writeNode(expectedTx.newNode(createItems("0", "1", "3", "4"), []pgnum{})) 382 | 383 | expectedChild1 := expectedTx.writeNode(expectedTx.newNode(createItems("6", "7"), []pgnum{})) 384 | 385 | expectedRoot := expectedTx.writeNode(expectedTx.newNode(createItems("5"), []pgnum{expectedChild0.pageNum, expectedChild1.pageNum})) 386 | 387 | expectedCollection, err := expectedTx.createCollection(newCollection(testCollectionName, expectedRoot.pageNum)) 388 | require.NoError(t, err) 389 | 390 | err = expectedTx.Commit() 391 | require.NoError(t, err) 392 | 393 | areTreesEqual(t, expectedCollection, collection) 394 | } 395 | 396 | // Test_RemoveFromRootAndRebalanceMergeFromUnbalanced tests when the unbalanced node is not the most left one so the 397 | // merge has to happen from the unbalanced node to the node left to it 398 | func Test_RemoveFromRootAndRebalanceMergeFromUnbalanced(t *testing.T) { 399 | db, cleanFunc := createTestDB(t) 400 | defer cleanFunc() 401 | 402 | tx := db.WriteTx() 403 | 404 | child0 := tx.writeNode(tx.newNode(createItems("0", "1"), []pgnum{})) 405 | 406 | child1 := tx.writeNode(tx.newNode(createItems("3", "4"), []pgnum{})) 407 | 408 | child2 := tx.writeNode(tx.newNode(createItems("6", "7"), []pgnum{})) 409 | 410 | root := tx.writeNode(tx.newNode(createItems("2", "5"), []pgnum{child0.pageNum, child1.pageNum, child2.pageNum})) 411 | 412 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 413 | require.NoError(t, err) 414 | 415 | // Remove an element 416 | err = collection.Remove(createItem("5")) 417 | require.NoError(t, err) 418 | 419 | err = tx.Commit() 420 | require.NoError(t, err) 421 | 422 | expectedDB, expectedCleanFunc := createTestDB(t) 423 | defer expectedCleanFunc() 424 | 425 | expectedTx := expectedDB.WriteTx() 426 | 427 | expectedChild0 := expectedTx.writeNode(expectedTx.newNode(createItems("0", "1", "2", "3"), []pgnum{})) 428 | 429 | expectedChild1 := expectedTx.writeNode(expectedTx.newNode(createItems("6", "7"), []pgnum{})) 430 | 431 | expectedRoot := expectedTx.writeNode(expectedTx.newNode(createItems("4"), []pgnum{expectedChild0.pageNum, expectedChild1.pageNum})) 432 | 433 | expectedCollection, err := expectedTx.createCollection(newCollection(testCollectionName, expectedRoot.pageNum)) 434 | require.NoError(t, err) 435 | 436 | err = expectedTx.Commit() 437 | require.NoError(t, err) 438 | 439 | // Remove an element 440 | areTreesEqual(t, expectedCollection, collection) 441 | } 442 | 443 | func Test_RemoveFromInnerNodeAndRotateLeft(t *testing.T) { 444 | db, cleanFunc := createTestDB(t) 445 | defer cleanFunc() 446 | 447 | tx := db.WriteTx() 448 | 449 | child00 := tx.writeNode(tx.newNode(createItems("0", "1"), []pgnum{})) 450 | 451 | child01 := tx.writeNode(tx.newNode(createItems("3", "4"), []pgnum{})) 452 | 453 | child02 := tx.writeNode(tx.newNode(createItems("6", "7"), []pgnum{})) 454 | 455 | child0 := tx.writeNode(tx.newNode(createItems("2", "5"), []pgnum{child00.pageNum, child01.pageNum, child02.pageNum})) 456 | 457 | child10 := tx.writeNode(tx.newNode(createItems("9", "a"), []pgnum{})) 458 | 459 | child11 := tx.writeNode(tx.newNode(createItems("c", "d"), []pgnum{})) 460 | 461 | child12 := tx.writeNode(tx.newNode(createItems("f", "g"), []pgnum{})) 462 | 463 | child13 := tx.writeNode(tx.newNode(createItems("i", "j"), []pgnum{})) 464 | 465 | child1 := tx.writeNode(tx.newNode(createItems("b", "e", "h"), []pgnum{child10.pageNum, child11.pageNum, child12.pageNum, child13.pageNum})) 466 | 467 | root := tx.writeNode(tx.newNode(createItems("8"), []pgnum{child0.pageNum, child1.pageNum})) 468 | 469 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 470 | require.NoError(t, err) 471 | 472 | // Remove an element 473 | err = collection.Remove(createItem("5")) 474 | require.NoError(t, err) 475 | 476 | err = tx.Commit() 477 | require.NoError(t, err) 478 | 479 | expectedDB, expectedCleanFunc := createTestDB(t) 480 | defer expectedCleanFunc() 481 | 482 | expectedTx := expectedDB.WriteTx() 483 | 484 | expectedChild00 := expectedTx.writeNode(expectedTx.newNode(createItems("0", "1", "2", "3"), []pgnum{})) 485 | 486 | expectedChild01 := expectedTx.writeNode(expectedTx.newNode(createItems("6", "7"), []pgnum{})) 487 | 488 | expectedChild02 := expectedTx.writeNode(expectedTx.newNode(createItems("9", "a"), []pgnum{})) 489 | 490 | expectedChild0 := expectedTx.writeNode(expectedTx.newNode(createItems("4", "8"), []pgnum{expectedChild00.pageNum, expectedChild01.pageNum, expectedChild02.pageNum})) 491 | 492 | expectedChild10 := expectedTx.writeNode(expectedTx.newNode(createItems("c", "d"), []pgnum{})) 493 | 494 | expectedChild11 := expectedTx.writeNode(expectedTx.newNode(createItems("f", "g"), []pgnum{})) 495 | 496 | expectedChild12 := expectedTx.writeNode(expectedTx.newNode(createItems("i", "j"), []pgnum{})) 497 | 498 | expectedChild1 := expectedTx.writeNode(expectedTx.newNode(createItems("e", "h"), []pgnum{expectedChild10.pageNum, expectedChild11.pageNum, expectedChild12.pageNum})) 499 | 500 | expectedRoot := expectedTx.writeNode(expectedTx.newNode(createItems("b"), []pgnum{expectedChild0.pageNum, expectedChild1.pageNum})) 501 | 502 | expectedCollection, err := expectedTx.createCollection(newCollection(testCollectionName, expectedRoot.pageNum)) 503 | require.NoError(t, err) 504 | 505 | err = expectedTx.Commit() 506 | require.NoError(t, err) 507 | 508 | // Remove an element 509 | areTreesEqual(t, expectedCollection, collection) 510 | } 511 | 512 | func Test_RemoveFromInnerNodeAndRotateRight(t *testing.T) { 513 | db, cleanFunc := createTestDB(t) 514 | defer cleanFunc() 515 | 516 | tx := db.WriteTx() 517 | 518 | child00 := tx.writeNode(tx.newNode(createItems("0", "1"), []pgnum{})) 519 | 520 | child01 := tx.writeNode(tx.newNode(createItems("3", "4"), []pgnum{})) 521 | 522 | child02 := tx.writeNode(tx.newNode(createItems("6", "7"), []pgnum{})) 523 | 524 | child03 := tx.writeNode(tx.newNode(createItems("9", "a"), []pgnum{})) 525 | 526 | child0 := tx.writeNode(tx.newNode(createItems("2", "5", "8"), []pgnum{child00.pageNum, child01.pageNum, child02.pageNum, child03.pageNum})) 527 | 528 | child10 := tx.writeNode(tx.newNode(createItems("c", "d"), []pgnum{})) 529 | 530 | child11 := tx.writeNode(tx.newNode(createItems("f", "g"), []pgnum{})) 531 | 532 | child12 := tx.writeNode(tx.newNode(createItems("i", "j"), []pgnum{})) 533 | 534 | child1 := tx.writeNode(tx.newNode(createItems("e", "h"), []pgnum{child10.pageNum, child11.pageNum, child12.pageNum})) 535 | 536 | root := tx.writeNode(tx.newNode(createItems("b"), []pgnum{child0.pageNum, child1.pageNum})) 537 | 538 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 539 | require.NoError(t, err) 540 | 541 | // Remove an element 542 | err = collection.Remove(createItem("e")) 543 | require.NoError(t, err) 544 | 545 | err = tx.Commit() 546 | require.NoError(t, err) 547 | 548 | expectedDB, expectedCleanFunc := createTestDB(t) 549 | defer expectedCleanFunc() 550 | 551 | expectedTx := expectedDB.WriteTx() 552 | 553 | expectedChild00 := expectedTx.writeNode(expectedTx.newNode(createItems("0", "1"), []pgnum{})) 554 | 555 | expectedChild01 := expectedTx.writeNode(expectedTx.newNode(createItems("3", "4"), []pgnum{})) 556 | 557 | expectedChild02 := expectedTx.writeNode(expectedTx.newNode(createItems("6", "7"), []pgnum{})) 558 | 559 | expectedChild0 := expectedTx.writeNode(expectedTx.newNode(createItems("2", "5"), []pgnum{expectedChild00.pageNum, expectedChild01.pageNum, expectedChild02.pageNum})) 560 | 561 | expectedChild10 := expectedTx.writeNode(expectedTx.newNode(createItems("9", "a"), []pgnum{})) 562 | 563 | expectedChild11 := expectedTx.writeNode(expectedTx.newNode(createItems("c", "d", "f", "g"), []pgnum{})) 564 | 565 | expectedChild12 := expectedTx.writeNode(expectedTx.newNode(createItems("i", "j"), []pgnum{})) 566 | 567 | expectedChild1 := expectedTx.writeNode(expectedTx.newNode(createItems("b", "h"), []pgnum{expectedChild10.pageNum, expectedChild11.pageNum, expectedChild12.pageNum})) 568 | 569 | expectedRoot := expectedTx.writeNode(expectedTx.newNode(createItems("8"), []pgnum{expectedChild0.pageNum, expectedChild1.pageNum})) 570 | 571 | expectedCollection, err := expectedTx.createCollection(newCollection(testCollectionName, expectedRoot.pageNum)) 572 | require.NoError(t, err) 573 | 574 | err = expectedTx.Commit() 575 | require.NoError(t, err) 576 | 577 | // Remove an element 578 | areTreesEqual(t, expectedCollection, collection) 579 | } 580 | 581 | func Test_RemoveFromInnerNodeAndUnion(t *testing.T) { 582 | db, cleanFunc := createTestDB(t) 583 | defer cleanFunc() 584 | 585 | tx := db.WriteTx() 586 | 587 | child00 := tx.writeNode(tx.newNode(createItems("0", "1"), []pgnum{})) 588 | 589 | child01 := tx.writeNode(tx.newNode(createItems("3", "4"), []pgnum{})) 590 | 591 | child02 := tx.writeNode(tx.newNode(createItems("6", "7"), []pgnum{})) 592 | 593 | child0 := tx.writeNode(tx.newNode(createItems("2", "5"), []pgnum{child00.pageNum, child01.pageNum, child02.pageNum})) 594 | 595 | child10 := tx.writeNode(tx.newNode(createItems("9", "a"), []pgnum{})) 596 | 597 | child11 := tx.writeNode(tx.newNode(createItems("c", "d"), []pgnum{})) 598 | 599 | child12 := tx.writeNode(tx.newNode(createItems("f", "g"), []pgnum{})) 600 | 601 | child1 := tx.writeNode(tx.newNode(createItems("b", "e"), []pgnum{child10.pageNum, child11.pageNum, child12.pageNum})) 602 | 603 | root := tx.writeNode(tx.newNode(createItems("8"), []pgnum{child0.pageNum, child1.pageNum})) 604 | 605 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 606 | require.NoError(t, err) 607 | 608 | // Remove an element 609 | err = collection.Remove(createItem("2")) 610 | require.NoError(t, err) 611 | 612 | err = tx.Commit() 613 | require.NoError(t, err) 614 | 615 | expectedDB, expectedCleanFunc := createTestDB(t) 616 | defer expectedCleanFunc() 617 | 618 | expectedTx := expectedDB.WriteTx() 619 | 620 | expectedChild0 := expectedTx.writeNode(expectedTx.newNode(createItems("0", "1", "3", "4"), []pgnum{})) 621 | 622 | expectedChild1 := expectedTx.writeNode(expectedTx.newNode(createItems("6", "7"), []pgnum{})) 623 | 624 | expectedChild2 := expectedTx.writeNode(expectedTx.newNode(createItems("9", "a"), []pgnum{})) 625 | 626 | expectedChild3 := expectedTx.writeNode(expectedTx.newNode(createItems("c", "d"), []pgnum{})) 627 | 628 | expectedChild4 := expectedTx.writeNode(expectedTx.newNode(createItems("f", "g"), []pgnum{})) 629 | 630 | expectedRoot := expectedTx.writeNode(expectedTx.newNode(createItems("5", "8", "b", "e"), []pgnum{expectedChild0.pageNum, expectedChild1.pageNum, expectedChild2.pageNum, expectedChild3.pageNum, expectedChild4.pageNum})) 631 | 632 | expectedCollection, err := expectedTx.createCollection(newCollection(testCollectionName, expectedRoot.pageNum)) 633 | require.NoError(t, err) 634 | 635 | err = expectedTx.Commit() 636 | require.NoError(t, err) 637 | 638 | // Remove an element 639 | areTreesEqual(t, expectedCollection, collection) 640 | } 641 | 642 | func Test_RemoveFromLeafAndRotateLeft(t *testing.T) { 643 | db, cleanFunc := createTestDB(t) 644 | defer cleanFunc() 645 | 646 | tx := db.WriteTx() 647 | 648 | child00 := tx.writeNode(tx.newNode(createItems("0", "1"), []pgnum{})) 649 | 650 | child01 := tx.writeNode(tx.newNode(createItems("3", "4", "5"), []pgnum{})) 651 | 652 | child02 := tx.writeNode(tx.newNode(createItems("7", "8"), []pgnum{})) 653 | 654 | child0 := tx.writeNode(tx.newNode(createItems("2", "6"), []pgnum{child00.pageNum, child01.pageNum, child02.pageNum})) 655 | 656 | child10 := tx.writeNode(tx.newNode(createItems("a", "b"), []pgnum{})) 657 | 658 | child11 := tx.writeNode(tx.newNode(createItems("d", "e"), []pgnum{})) 659 | 660 | child12 := tx.writeNode(tx.newNode(createItems("g", "h"), []pgnum{})) 661 | 662 | child1 := tx.writeNode(tx.newNode(createItems("c", "f"), []pgnum{child10.pageNum, child11.pageNum, child12.pageNum})) 663 | 664 | root := tx.writeNode(tx.newNode(createItems("9"), []pgnum{child0.pageNum, child1.pageNum})) 665 | 666 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 667 | require.NoError(t, err) 668 | 669 | // Remove an element 670 | err = collection.Remove(createItem("1")) 671 | require.NoError(t, err) 672 | 673 | err = tx.Commit() 674 | require.NoError(t, err) 675 | 676 | expectedDB, expectedCleanFunc := createTestDB(t) 677 | defer expectedCleanFunc() 678 | 679 | expectedTx := expectedDB.WriteTx() 680 | 681 | expectedChild00 := expectedTx.writeNode(expectedTx.newNode(createItems("0", "2"), []pgnum{})) 682 | 683 | expectedChild01 := expectedTx.writeNode(expectedTx.newNode(createItems("4", "5"), []pgnum{})) 684 | 685 | expectedChild02 := expectedTx.writeNode(expectedTx.newNode(createItems("7", "8"), []pgnum{})) 686 | 687 | expectedChild0 := expectedTx.writeNode(expectedTx.newNode(createItems("3", "6"), []pgnum{expectedChild00.pageNum, expectedChild01.pageNum, expectedChild02.pageNum})) 688 | 689 | expectedChild10 := expectedTx.writeNode(expectedTx.newNode(createItems("a", "b"), []pgnum{})) 690 | 691 | expectedChild11 := expectedTx.writeNode(expectedTx.newNode(createItems("d", "e"), []pgnum{})) 692 | 693 | expectedChild12 := expectedTx.writeNode(expectedTx.newNode(createItems("g", "h"), []pgnum{})) 694 | 695 | expectedChild1 := expectedTx.writeNode(expectedTx.newNode(createItems("c", "f"), []pgnum{expectedChild10.pageNum, expectedChild11.pageNum, expectedChild12.pageNum})) 696 | 697 | expectedRoot := expectedTx.writeNode(expectedTx.newNode(createItems("9"), []pgnum{expectedChild0.pageNum, expectedChild1.pageNum})) 698 | 699 | expectedCollection, err := expectedTx.createCollection(newCollection(testCollectionName, expectedRoot.pageNum)) 700 | require.NoError(t, err) 701 | 702 | err = expectedTx.Commit() 703 | require.NoError(t, err) 704 | 705 | // Remove an element 706 | areTreesEqual(t, expectedCollection, collection) 707 | } 708 | 709 | func Test_RemoveFromLeafAndRotateRight(t *testing.T) { 710 | db, cleanFunc := createTestDB(t) 711 | defer cleanFunc() 712 | 713 | tx := db.WriteTx() 714 | 715 | child00 := tx.writeNode(tx.newNode(createItems("0", "1"), []pgnum{})) 716 | 717 | child01 := tx.writeNode(tx.newNode(createItems("3", "4", "5"), []pgnum{})) 718 | 719 | child02 := tx.writeNode(tx.newNode(createItems("7", "8"), []pgnum{})) 720 | 721 | child0 := tx.writeNode(tx.newNode(createItems("2", "6"), []pgnum{child00.pageNum, child01.pageNum, child02.pageNum})) 722 | 723 | child10 := tx.writeNode(tx.newNode(createItems("a", "b"), []pgnum{})) 724 | 725 | child11 := tx.writeNode(tx.newNode(createItems("d", "e"), []pgnum{})) 726 | 727 | child12 := tx.writeNode(tx.newNode(createItems("g", "h"), []pgnum{})) 728 | 729 | child1 := tx.writeNode(tx.newNode(createItems("c", "f"), []pgnum{child10.pageNum, child11.pageNum, child12.pageNum})) 730 | 731 | root := tx.writeNode(tx.newNode(createItems("9"), []pgnum{child0.pageNum, child1.pageNum})) 732 | 733 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 734 | require.NoError(t, err) 735 | 736 | // Remove an element 737 | err = collection.Remove(createItem("8")) 738 | require.NoError(t, err) 739 | 740 | err = tx.Commit() 741 | require.NoError(t, err) 742 | 743 | expectedDB, expectedCleanFunc := createTestDB(t) 744 | defer expectedCleanFunc() 745 | 746 | expectedTx := expectedDB.WriteTx() 747 | 748 | expectedChild00 := expectedTx.writeNode(expectedTx.newNode(createItems("0", "1"), []pgnum{})) 749 | 750 | expectedChild01 := expectedTx.writeNode(expectedTx.newNode(createItems("3", "4"), []pgnum{})) 751 | 752 | expectedChild02 := expectedTx.writeNode(expectedTx.newNode(createItems("6", "7"), []pgnum{})) 753 | 754 | expectedChild0 := expectedTx.writeNode(expectedTx.newNode(createItems("2", "5"), []pgnum{expectedChild00.pageNum, expectedChild01.pageNum, expectedChild02.pageNum})) 755 | 756 | expectedChild10 := expectedTx.writeNode(expectedTx.newNode(createItems("a", "b"), []pgnum{})) 757 | 758 | expectedChild11 := expectedTx.writeNode(expectedTx.newNode(createItems("d", "e"), []pgnum{})) 759 | 760 | expectedChild12 := expectedTx.writeNode(expectedTx.newNode(createItems("g", "h"), []pgnum{})) 761 | 762 | expectedChild1 := expectedTx.writeNode(expectedTx.newNode(createItems("c", "f"), []pgnum{expectedChild10.pageNum, expectedChild11.pageNum, expectedChild12.pageNum})) 763 | 764 | expectedRoot := expectedTx.writeNode(expectedTx.newNode(createItems("9"), []pgnum{expectedChild0.pageNum, expectedChild1.pageNum})) 765 | 766 | expectedCollection, err := expectedTx.createCollection(newCollection(testCollectionName, expectedRoot.pageNum)) 767 | require.NoError(t, err) 768 | 769 | err = expectedTx.Commit() 770 | require.NoError(t, err) 771 | 772 | // Remove an element 773 | areTreesEqual(t, expectedCollection, collection) 774 | } 775 | 776 | func Test_RemoveFromLeafAndUnion(t *testing.T) { 777 | db, cleanFunc := createTestDB(t) 778 | defer cleanFunc() 779 | 780 | tx := db.WriteTx() 781 | 782 | child00 := tx.writeNode(tx.newNode(createItems("0", "1"), []pgnum{})) 783 | 784 | child01 := tx.writeNode(tx.newNode(createItems("3", "4"), []pgnum{})) 785 | 786 | child02 := tx.writeNode(tx.newNode(createItems("6", "7"), []pgnum{})) 787 | 788 | child0 := tx.writeNode(tx.newNode(createItems("2", "5"), []pgnum{child00.pageNum, child01.pageNum, child02.pageNum})) 789 | 790 | child10 := tx.writeNode(tx.newNode(createItems("9", "a"), []pgnum{})) 791 | 792 | child11 := tx.writeNode(tx.newNode(createItems("c", "d"), []pgnum{})) 793 | 794 | child12 := tx.writeNode(tx.newNode(createItems("f", "g"), []pgnum{})) 795 | 796 | child1 := tx.writeNode(tx.newNode(createItems("b", "e"), []pgnum{child10.pageNum, child11.pageNum, child12.pageNum})) 797 | 798 | root := tx.writeNode(tx.newNode(createItems("8"), []pgnum{child0.pageNum, child1.pageNum})) 799 | 800 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 801 | require.NoError(t, err) 802 | 803 | // Remove an element 804 | err = collection.Remove(createItem("0")) 805 | require.NoError(t, err) 806 | 807 | err = tx.Commit() 808 | require.NoError(t, err) 809 | 810 | expectedDB, expectedCleanFunc := createTestDB(t) 811 | defer expectedCleanFunc() 812 | 813 | expectedTx := expectedDB.WriteTx() 814 | 815 | expectedChild0 := expectedTx.writeNode(expectedTx.newNode(createItems("1", "2", "3", "4"), []pgnum{})) 816 | 817 | expectedChild1 := expectedTx.writeNode(expectedTx.newNode(createItems("6", "7"), []pgnum{})) 818 | 819 | expectedChild2 := expectedTx.writeNode(expectedTx.newNode(createItems("9", "a"), []pgnum{})) 820 | 821 | expectedChild3 := expectedTx.writeNode(expectedTx.newNode(createItems("c", "d"), []pgnum{})) 822 | 823 | expectedChild4 := expectedTx.writeNode(expectedTx.newNode(createItems("f", "g"), []pgnum{})) 824 | 825 | expectedRoot := expectedTx.writeNode(expectedTx.newNode(createItems("5", "8", "b", "e"), []pgnum{expectedChild0.pageNum, expectedChild1.pageNum, expectedChild2.pageNum, expectedChild3.pageNum, expectedChild4.pageNum})) 826 | 827 | expectedCollection, err := expectedTx.createCollection(newCollection(testCollectionName, expectedRoot.pageNum)) 828 | require.NoError(t, err) 829 | 830 | err = expectedTx.Commit() 831 | require.NoError(t, err) 832 | 833 | // Remove an element 834 | areTreesEqual(t, expectedCollection, collection) 835 | } 836 | 837 | func Test_FindNode(t *testing.T) { 838 | db, cleanFunc := createTestDB(t) 839 | defer cleanFunc() 840 | 841 | tx := db.WriteTx() 842 | 843 | child00 := tx.writeNode(tx.newNode(createItems("0", "1"), []pgnum{})) 844 | 845 | child01 := tx.writeNode(tx.newNode(createItems("3", "4"), []pgnum{})) 846 | 847 | child02 := tx.writeNode(tx.newNode(createItems("6", "7"), []pgnum{})) 848 | 849 | child0 := tx.writeNode(tx.newNode(createItems("2", "5"), []pgnum{child00.pageNum, child01.pageNum, child02.pageNum})) 850 | 851 | child10 := tx.writeNode(tx.newNode(createItems("9", "a"), []pgnum{})) 852 | 853 | child11 := tx.writeNode(tx.newNode(createItems("c", "d"), []pgnum{})) 854 | 855 | child12 := tx.writeNode(tx.newNode(createItems("f", "g"), []pgnum{})) 856 | 857 | child1 := tx.writeNode(tx.newNode(createItems("b", "e"), []pgnum{child10.pageNum, child11.pageNum, child12.pageNum})) 858 | 859 | root := tx.writeNode(tx.newNode(createItems("8"), []pgnum{child0.pageNum, child1.pageNum})) 860 | 861 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 862 | require.NoError(t, err) 863 | 864 | err = tx.Commit() 865 | require.NoError(t, err) 866 | 867 | // Item found 868 | expectedVal := createItem("c") 869 | expectedItem := newItem(expectedVal, expectedVal) 870 | item, err := collection.Find(expectedVal) 871 | require.NoError(t, err) 872 | assert.Equal(t, expectedItem, item) 873 | 874 | // Item not found 875 | expectedVal = createItem("h") 876 | item, err = collection.Find(expectedVal) 877 | require.NoError(t, err) 878 | assert.Nil(t, item) 879 | } 880 | 881 | func Test_UpdateNode(t *testing.T) { 882 | db, cleanFunc := createTestDB(t) 883 | defer cleanFunc() 884 | 885 | tx := db.WriteTx() 886 | 887 | child00 := tx.writeNode(tx.newNode(createItems("0", "1"), []pgnum{})) 888 | 889 | child01 := tx.writeNode(tx.newNode(createItems("3", "4"), []pgnum{})) 890 | 891 | child02 := tx.writeNode(tx.newNode(createItems("6", "7"), []pgnum{})) 892 | 893 | child0 := tx.writeNode(tx.newNode(createItems("2", "5"), []pgnum{child00.pageNum, child01.pageNum, child02.pageNum})) 894 | 895 | child10 := tx.writeNode(tx.newNode(createItems("9", "a"), []pgnum{})) 896 | 897 | child11 := tx.writeNode(tx.newNode(createItems("c", "d"), []pgnum{})) 898 | 899 | child12 := tx.writeNode(tx.newNode(createItems("f", "g"), []pgnum{})) 900 | 901 | child1 := tx.writeNode(tx.newNode(createItems("b", "e"), []pgnum{child10.pageNum, child11.pageNum, child12.pageNum})) 902 | 903 | root := tx.writeNode(tx.newNode(createItems("8"), []pgnum{child0.pageNum, child1.pageNum})) 904 | 905 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 906 | require.NoError(t, err) 907 | 908 | err = tx.Commit() 909 | require.NoError(t, err) 910 | 911 | tx2 := db.WriteTx() 912 | collection, err = tx2.GetCollection(collection.name) 913 | require.NoError(t, err) 914 | 915 | // Item found 916 | expectedVal := createItem("c") 917 | expectedItem := newItem(expectedVal, expectedVal) 918 | item, err := collection.Find(expectedVal) 919 | require.NoError(t, err) 920 | assert.Equal(t, expectedItem, item) 921 | 922 | // Item updated successfully 923 | newvalue := createItem("f") 924 | err = collection.Put(expectedVal, newvalue) 925 | require.NoError(t, err) 926 | 927 | item, err = collection.Find(expectedVal) 928 | require.NoError(t, err) 929 | assert.Equal(t, newvalue, item.value) 930 | 931 | err = tx2.Commit() 932 | require.NoError(t, err) 933 | } 934 | 935 | func TestSerializeWithoutChildNodes(t *testing.T) { 936 | items := []*Item{newItem([]byte("key1"), []byte("val1")), newItem([]byte("key2"), []byte("val2"))} 937 | var childNodes []pgnum 938 | node := &Node{ 939 | items: items, 940 | childNodes: childNodes, 941 | } 942 | 943 | actual := node.serialize(make([]byte, testPageSize, testPageSize)) 944 | 945 | expectedPage, err := os.ReadFile(getExpectedResultFileName(t.Name())) 946 | require.NoError(t, err) 947 | assert.Equal(t, 0, bytes.Compare(actual, expectedPage)) 948 | } 949 | 950 | func TestDeserializeWithoutChildNodes(t *testing.T) { 951 | page, err := os.ReadFile(getExpectedResultFileName(t.Name())) 952 | require.NoError(t, err) 953 | 954 | actualNode := NewEmptyNode() 955 | actualNode.deserialize(page) 956 | 957 | items := []*Item{newItem([]byte("key1"), []byte("val1")), newItem([]byte("key2"), []byte("val2"))} 958 | var childNodes []pgnum 959 | expectedNode := &Node{ 960 | items: items, 961 | childNodes: childNodes, 962 | } 963 | 964 | assert.Equal(t, expectedNode, actualNode) 965 | } 966 | 967 | func TestSerializeWithChildNodes(t *testing.T) { 968 | items := []*Item{newItem([]byte("key1"), []byte("val1")), newItem([]byte("key2"), []byte("val2"))} 969 | childNodes := []pgnum{1, 2, 3} 970 | node := &Node{ 971 | items: items, 972 | childNodes: childNodes, 973 | } 974 | 975 | actual := node.serialize(make([]byte, testPageSize, testPageSize)) 976 | 977 | expectedPage, err := os.ReadFile(getExpectedResultFileName(t.Name())) 978 | require.NoError(t, err) 979 | assert.Equal(t, 0, bytes.Compare(actual, expectedPage)) 980 | } 981 | 982 | func TestDeserializeWithChildNodes(t *testing.T) { 983 | page, err := os.ReadFile(getExpectedResultFileName(t.Name())) 984 | require.NoError(t, err) 985 | 986 | items := []*Item{newItem([]byte("key1"), []byte("val1")), newItem([]byte("key2"), []byte("val2"))} 987 | childNodes := []pgnum{1, 2, 3} 988 | expectedNode := &Node{ 989 | items: items, 990 | childNodes: childNodes, 991 | } 992 | 993 | actualNode := NewEmptyNode() 994 | actualNode.deserialize(page) 995 | assert.Equal(t, expectedNode, actualNode) 996 | } 997 | -------------------------------------------------------------------------------- /testutils.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import ( 4 | "bytes" 5 | "fmt" 6 | "github.com/google/uuid" 7 | "github.com/stretchr/testify/assert" 8 | "github.com/stretchr/testify/require" 9 | "os" 10 | "testing" 11 | ) 12 | 13 | const ( 14 | // The tests are designed so min items should be around 2 and max items should be around 4 (1 is not enough, 5 is 15 | // too much). The sizes are adjusted accordingly so those number will return in all tests. 16 | testPageSize = 4096 17 | testMinPercentage = 0.2 18 | testMaxPercentage = 0.55 19 | testValSize = 255 20 | 21 | mockNumberOfElements = 10 22 | expectedFolderPath = "expected" 23 | ) 24 | 25 | var ( 26 | testCollectionName = []byte("test1") 27 | ) 28 | 29 | func createTestDB(t *testing.T) (*DB, func()) { 30 | db, err := Open(getTempFileName(), &Options{MinFillPercent: testMinPercentage, MaxFillPercent: testMaxPercentage}) 31 | require.NoError(t, err) 32 | 33 | return db, func() { 34 | _ = db.Close() 35 | } 36 | } 37 | 38 | func areCollectionsEqual(t *testing.T, c1, c2 *Collection) { 39 | assert.Equal(t, c1.name, c2.name) 40 | assert.Equal(t, c1.root, c2.root) 41 | assert.Equal(t, c1.counter, c2.counter) 42 | } 43 | 44 | func areTreesEqual(t *testing.T, t1, t2 *Collection) { 45 | t1Root, err := t1.tx.getNode(t1.root) 46 | require.NoError(t, err) 47 | 48 | t2Root, err := t2.tx.getNode(t2.root) 49 | require.NoError(t, err) 50 | 51 | areTreesEqualHelper(t, t1Root, t2Root) 52 | } 53 | 54 | func areNodesEqual(t *testing.T, n1, n2 *Node) { 55 | for i := 0; i < len(n1.items); i++ { 56 | assert.Equal(t, n1.items[i].key, n2.items[i].key) 57 | assert.Equal(t, n1.items[i].value, n2.items[i].value) 58 | } 59 | } 60 | 61 | func areTreesEqualHelper(t *testing.T, n1, n2 *Node) { 62 | require.Equal(t, len(n1.items), len(n2.items)) 63 | require.Equal(t, len(n1.childNodes), len(n2.childNodes)) 64 | areNodesEqual(t, n1, n2) 65 | // Exit condition: child node -> len(n1.childNodes) == 0 66 | for i := 0; i < len(n1.childNodes); i++ { 67 | node1, err := n1.getNode(n1.childNodes[i]) 68 | require.NoError(t, err) 69 | node2, err := n2.getNode(n2.childNodes[i]) 70 | areTreesEqualHelper(t, node1, node2) 71 | } 72 | } 73 | 74 | func createTestMockTree(t *testing.T) (*Collection, func()) { 75 | db, cleanFunc := createTestDB(t) 76 | 77 | tx := db.WriteTx() 78 | 79 | child0 := tx.writeNode(tx.newNode(createItems("0", "1"), []pgnum{})) 80 | 81 | child1 := tx.writeNode(tx.newNode(createItems("3", "4"), []pgnum{})) 82 | 83 | child2 := tx.writeNode(tx.newNode(createItems("6", "7", "8", "9"), []pgnum{})) 84 | 85 | root := tx.writeNode(tx.newNode(createItems("2", "5"), []pgnum{child0.pageNum, child1.pageNum, child2.pageNum})) 86 | 87 | expectedCollection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 88 | require.NoError(t, err) 89 | 90 | err = tx.Commit() 91 | require.NoError(t, err) 92 | 93 | return expectedCollection, cleanFunc 94 | } 95 | 96 | func getExpectedResultFileName(name string) string { 97 | return fmt.Sprintf("%s%c%s", expectedFolderPath, os.PathSeparator, name) 98 | } 99 | 100 | func getTempFileName() string { 101 | var id = uuid.New() 102 | return fmt.Sprintf("%s%c%s", os.TempDir(), os.PathSeparator,id) 103 | } 104 | 105 | func memset(buf []byte, count int) []byte { 106 | return bytes.Repeat(buf, count) 107 | } 108 | 109 | // createItem creates an item by memset a fixed size buf (255) with the given value. The fixed size is used so all tests 110 | // so the minimum number of items in a node will be 2 and the maximum will be 4. This is for uniformity in the rebalance 111 | // tests. 112 | func createItem(key string) []byte { 113 | keyBuf := memset([]byte(key), testValSize) 114 | return keyBuf 115 | } 116 | 117 | func createItems(keys ...string) []*Item { 118 | items := make([]*Item, 0) 119 | for _, key := range keys { 120 | keyBuf := memset([]byte(key), testValSize) 121 | items = append(items, newItem(keyBuf, keyBuf)) 122 | } 123 | return items 124 | } 125 | -------------------------------------------------------------------------------- /tx.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | type tx struct { 4 | dirtyNodes map[pgnum]*Node 5 | pagesToDelete []pgnum 6 | 7 | // new pages allocated during the transaction. They will be released if rollback is called. 8 | allocatedPageNums []pgnum 9 | 10 | write bool 11 | 12 | db *DB 13 | } 14 | 15 | func newTx(db *DB, write bool) *tx { 16 | return &tx{ 17 | map[pgnum]*Node{}, 18 | make([]pgnum, 0), 19 | make([]pgnum, 0), 20 | write, 21 | db, 22 | } 23 | } 24 | 25 | func (tx *tx) newNode(items []*Item, childNodes []pgnum) *Node { 26 | node := NewEmptyNode() 27 | node.items = items 28 | node.childNodes = childNodes 29 | node.pageNum = tx.db.getNextPage() 30 | node.tx = tx 31 | 32 | node.tx.allocatedPageNums = append(node.tx.allocatedPageNums, node.pageNum) 33 | return node 34 | } 35 | 36 | func (tx *tx) getNode(pageNum pgnum) (*Node, error) { 37 | if node, ok := tx.dirtyNodes[pageNum]; ok { 38 | return node, nil 39 | } 40 | 41 | node, err := tx.db.getNode(pageNum) 42 | if err != nil { 43 | return nil, err 44 | } 45 | node.tx = tx 46 | return node, nil 47 | } 48 | 49 | func (tx *tx) writeNode(node *Node) *Node { 50 | tx.dirtyNodes[node.pageNum] = node 51 | node.tx = tx 52 | return node 53 | } 54 | 55 | func (tx *tx) deleteNode(node *Node) { 56 | tx.pagesToDelete = append(tx.pagesToDelete, node.pageNum) 57 | } 58 | 59 | func (tx *tx) Rollback() { 60 | if !tx.write { 61 | tx.db.rwlock.RUnlock() 62 | return 63 | } 64 | 65 | tx.dirtyNodes = nil 66 | tx.pagesToDelete = nil 67 | for _, pageNum := range tx.allocatedPageNums { 68 | tx.db.freelist.releasePage(pageNum) 69 | } 70 | tx.allocatedPageNums = nil 71 | tx.db.rwlock.Unlock() 72 | } 73 | 74 | func (tx *tx) Commit() error { 75 | if !tx.write { 76 | tx.db.rwlock.RUnlock() 77 | return nil 78 | } 79 | 80 | for _, node := range tx.dirtyNodes { 81 | _, err := tx.db.writeNode(node) 82 | if err != nil { 83 | return err 84 | } 85 | } 86 | 87 | for _, pageNum := range tx.pagesToDelete { 88 | tx.db.deleteNode(pageNum) 89 | } 90 | _, err := tx.db.writeFreelist() 91 | if err != nil { 92 | return err 93 | } 94 | 95 | tx.dirtyNodes = nil 96 | tx.pagesToDelete = nil 97 | tx.allocatedPageNums = nil 98 | tx.db.rwlock.Unlock() 99 | return nil 100 | } 101 | 102 | 103 | // This will be used for implementing COW. The idea is to mark all the dirty collection, then for each collection, 104 | // traverse it's dirty in post order and commit child page. Then take the new page numbers, assign them to the parent, 105 | // and save him as well and so. After we wrote all collections, rewrite the root node with the new collections roots. 106 | // Rewrite the freelist with the newly allocated pages. Finally, rewrite the meta page, so the new root node will take 107 | // effect. 108 | // COW will give us atomicity as new pages cannot be seen until the root node is written. This way, in case of a failure 109 | // or a rollback no harm will be done as nothing was committed to the database. 110 | //func (tx *tx) commitNode(node *Node) error { 111 | // oldPageNum := node.num 112 | // node.num = 0 113 | // 114 | // newNode, err := tx.db.writeNode(node) 115 | // if err != nil { 116 | // return err 117 | // } 118 | // tx.committedNodes[oldPageNum] = newNode.num 119 | // tx.deleteNode(node) 120 | // return nil 121 | //} 122 | // 123 | //// saveDirtyNodes saves the tree in a post order way. post order is used since child pages are written to the disk and 124 | //// are given new page id, only then we can update the parent node with new page of the child node. 125 | //func (tx *tx) saveDirtyNodes(node *Node) error { 126 | // if len(node.childNodes) == 0 { 127 | // return tx.commitNode(node) 128 | // } 129 | // 130 | // for i, childNodePgid := range node.childNodes { 131 | // if childNode, ok := tx.dirtyNodes[childNodePgid]; ok { 132 | // err := tx.saveDirtyNodes(childNode) 133 | // if err != nil { 134 | // return err 135 | // } 136 | // } 137 | // node.childNodes[i] = tx.committedNodes[childNodePgid] 138 | // } 139 | // 140 | // return tx.commitNode(node) 141 | //} 142 | 143 | func (tx *tx) getRootCollection() *Collection { 144 | rootCollection := newEmptyCollection() 145 | rootCollection.root = tx.db.root 146 | rootCollection.tx = tx 147 | return rootCollection 148 | } 149 | 150 | func (tx *tx) GetCollection(name []byte) (*Collection, error) { 151 | rootCollection := tx.getRootCollection() 152 | item, err := rootCollection.Find(name) 153 | if err != nil { 154 | return nil, err 155 | } 156 | 157 | if item == nil { 158 | return nil, nil 159 | } 160 | 161 | collection := newEmptyCollection() 162 | collection.deserialize(item) 163 | collection.tx = tx 164 | return collection, nil 165 | } 166 | 167 | func (tx *tx) CreateCollection(name []byte) (*Collection, error) { 168 | if !tx.write { 169 | return nil, writeInsideReadTxErr 170 | } 171 | 172 | newCollectionPage, err := tx.db.writeNode(NewEmptyNode()) 173 | if err != nil { 174 | return nil, err 175 | } 176 | 177 | newCollection := newEmptyCollection() 178 | newCollection.name = name 179 | newCollection.root = newCollectionPage.pageNum 180 | return tx.createCollection(newCollection) 181 | } 182 | 183 | func (tx *tx) DeleteCollection(name []byte) error { 184 | if !tx.write { 185 | return writeInsideReadTxErr 186 | } 187 | 188 | rootCollection := tx.getRootCollection() 189 | 190 | return rootCollection.Remove(name) 191 | 192 | } 193 | 194 | func (tx *tx) createCollection(collection *Collection) (*Collection, error) { 195 | collection.tx = tx 196 | collectionBytes := collection.serialize() 197 | 198 | rootCollection := tx.getRootCollection() 199 | err := rootCollection.Put(collection.name, collectionBytes.value) 200 | if err != nil { 201 | return nil, err 202 | } 203 | 204 | return collection, nil 205 | } 206 | -------------------------------------------------------------------------------- /tx_test.go: -------------------------------------------------------------------------------- 1 | package LibraDB 2 | 3 | import ( 4 | "github.com/stretchr/testify/assert" 5 | "github.com/stretchr/testify/require" 6 | "sync" 7 | "testing" 8 | ) 9 | 10 | func TestTx_CreateCollection(t *testing.T) { 11 | db, cleanFunc := createTestDB(t) 12 | defer cleanFunc() 13 | 14 | tx := db.WriteTx() 15 | collection, err := tx.CreateCollection(testCollectionName) 16 | require.NoError(t, err) 17 | 18 | err = tx.Commit() 19 | require.NoError(t, err) 20 | 21 | tx = db.ReadTx() 22 | actualCollection, err := tx.GetCollection(collection.name) 23 | require.NoError(t, err) 24 | 25 | err = tx.Commit() 26 | require.NoError(t, err) 27 | 28 | areCollectionsEqual(t, collection, actualCollection) 29 | } 30 | 31 | func TestTx_CreateCollectionReadTx(t *testing.T) { 32 | db, cleanFunc := createTestDB(t) 33 | defer cleanFunc() 34 | 35 | tx := db.ReadTx() 36 | collection, err := tx.CreateCollection(testCollectionName) 37 | require.Error(t, err) 38 | require.Nil(t, collection) 39 | 40 | err = tx.Commit() 41 | } 42 | 43 | func TestTx_OpenMultipleReadTxSimultaneously(t *testing.T) { 44 | db, cleanFunc := createTestDB(t) 45 | defer cleanFunc() 46 | 47 | tx1 := db.ReadTx() 48 | tx2 := db.ReadTx() 49 | 50 | collection1, err := tx1.GetCollection(testCollectionName) 51 | require.NoError(t, err) 52 | require.Nil(t, collection1) 53 | 54 | collection2, err := tx2.GetCollection(testCollectionName) 55 | require.NoError(t, err) 56 | require.Nil(t, collection2) 57 | 58 | err = tx1.Commit() 59 | err = tx2.Commit() 60 | } 61 | 62 | // TestTx_OpenReadAndWriteTxSimultaneously Validates read and write tx don't run simultaneously. It first starts a read 63 | // tx, then once the lock was acquired, a write transaction is started. Once the read tx finishes, the lock is released, 64 | // and the write tx start executing. Once the lock is acquired again, a read tx is triggered. 65 | // The nesting of the functions is done to make sure the transactions are fired only after the lock is acquired to avoid 66 | // race conditions. 67 | // We expect the first read tx (tx1) not to see the changes done by the write tx (tx2) even when though it queries the database 68 | // after the write tx was triggered (Because of the lock). 69 | // And again, even though tx3 was triggered before tx2 committed the changes, it doesn't query the database yet since 70 | // the lock is already acquired. It will query the database only after tx2 makes the changes and releases the lock. 71 | func TestTx_OpenReadAndWriteTxSimultaneously(t *testing.T) { 72 | db, cleanFunc := createTestDB(t) 73 | defer cleanFunc() 74 | 75 | wg := sync.WaitGroup{} 76 | 77 | tx1 := db.ReadTx() 78 | 79 | // Start write tx only after the lock was acquired by the read tx 80 | wg.Add(1) 81 | go func() { 82 | tx2 := db.WriteTx() 83 | 84 | // Start read tx only after the lock was acquired by the write tx 85 | wg.Add(1) 86 | go func() { 87 | tx3 := db.ReadTx() 88 | 89 | collection3, err := tx3.GetCollection(testCollectionName) 90 | require.NoError(t, err) 91 | require.Equal(t, testCollectionName, collection3.name) 92 | 93 | err = tx3.Commit() 94 | wg.Done() 95 | }() 96 | 97 | 98 | _, err := tx2.CreateCollection(testCollectionName) 99 | require.NoError(t, err) 100 | 101 | err = tx2.Commit() 102 | wg.Done() 103 | }() 104 | 105 | collection1, err := tx1.GetCollection(testCollectionName) 106 | require.NoError(t, err) 107 | require.Nil(t, collection1) 108 | 109 | err = tx1.Commit() 110 | 111 | wg.Wait() 112 | } 113 | 114 | func TestTx_Rollback(t *testing.T) { 115 | db, cleanFunc := createTestDB(t) 116 | defer cleanFunc() 117 | 118 | tx := db.WriteTx() 119 | child0 := tx.writeNode(tx.newNode(createItems("0", "1", "2", "3"), []pgnum{})) 120 | 121 | child1 := tx.writeNode(tx.newNode(createItems("5", "6", "7", "8"), []pgnum{})) 122 | 123 | root := tx.writeNode(tx.newNode(createItems("4"), []pgnum{child0.pageNum, child1.pageNum})) 124 | 125 | collection, err := tx.createCollection(newCollection(testCollectionName, root.pageNum)) 126 | require.NoError(t, err) 127 | 128 | err = tx.Commit() 129 | require.NoError(t, err) 130 | 131 | assert.Len(t, tx.db.freelist.releasedPages, 0) 132 | 133 | // Try to add 9 but then perform a rollback, so it won't be saved 134 | tx2 := db.WriteTx() 135 | 136 | collection, err = tx2.GetCollection(collection.name) 137 | require.NoError(t, err) 138 | 139 | val := createItem("9") 140 | err = collection.Put(val, val) 141 | require.NoError(t, err) 142 | 143 | tx2.Rollback() 144 | 145 | // 9 should not exist since a rollback was performed. A new page should be added to released page ids though, since 146 | // a split occurred and a new page node was created, but later deleted. 147 | assert.Len(t, tx2.db.freelist.releasedPages, 1) 148 | tx3 := db.ReadTx() 149 | 150 | collection, err = tx3.GetCollection(collection.name) 151 | require.NoError(t, err) 152 | 153 | // Item not found 154 | expectedVal := createItem("9") 155 | item, err := collection.Find(expectedVal) 156 | require.NoError(t, err) 157 | assert.Nil(t, item) 158 | 159 | err = tx3.Commit() 160 | require.NoError(t, err) 161 | 162 | assert.Len(t, tx3.db.freelist.releasedPages, 1) 163 | } 164 | --------------------------------------------------------------------------------