KVS module provides user level interface for console commands.
30 | It has discovery, data manipulation and retrival features. Under the hood
31 | it handles configurable run-time backends for each supported database.
Searches the record by an indexed field and a given value.
58 |
59 |
60 |
SEQ
61 |
Sequence table id_seq stores the counter per thing.
62 | The counters are global and atomic in each supported database.
63 | Sequences are used to generate unique names for records per distributed table.
64 | If names in the table are not unique, e.g.
65 | then count function may return a different value than the current sequence.
Increments and returns id counter for the particular table.
71 |
count(atom()) -> integer().
72 |
Returns number of records in table.
73 |
74 |
75 |
SETUP
76 |
In sys.config you can specify main kvs backend module as dba parameter
77 | and list of modules containing metainfo/0 exported function. For the
78 | stream operations you can specify the stream kvs backend module dba_st parameter.
FS is a filesystem backend implementation for KVS.
28 | Put the {dba,kvs_fs} property for the kvs application in your sys.config.
29 |
30 |
31 |
EXAMPLES
32 |
33 |
All examples can be executed in Erlang REPL. Only
34 | requirement is to have kvs set in dependencies and kvs application
35 | started.
36 |
37 |
Create a new kvs_fs table called test. When executed, this
38 | function will create a new directory called test under data
39 | directory in the current workspace.
Put a new key/value in table test. When executed, a new file is
48 | created under test directory. Its name is based on the sha1 of
49 | the key encoded in base64.
ROCKS is the RocksDB backend implementation for KVS.
26 | Put the {dba,kvs_rocks} and (optionally) {dba_st,kvs_st} properties
27 | for the kvs application in your sys.config.
The ST module provides STREAM interface for ROCKS backend.
36 | Set the {dba,kvs_rocks} along with {dba_st,kvs_st} in
37 | order to use ST module for stream operations.
You can grab kvs_stream
48 | and use it in your applications without importing synrc/kvs dependency,
49 | as this module is self-containing.
50 | The possible applications are: public and private feeds, FIFO queues,
51 | unread messages, chat applications, blockchain etc.
52 |
53 |
54 |
WRITER
55 |
56 |
Writer cursor represents unique append list chain with some cached values.
57 | E.g., elements count, first element of the chain, cache field for value of
58 | a previous written message and args field for passing arguments in fixpoint style.
Reader cursor represents a user reading pointer to the writer feed.
113 | Field #reader.feed is linked to #writer.id.
114 | The pos field represents current position in feed.
115 | Field dir is used for changing take and drop directions.
Moves cursor to next. Consume data down from top.
148 | Return error if list is empty, otherwise next element or last.
149 |
150 |
prev(#reader{}) -> #reader{}.
151 |
Moves cursor to prev. Consume data up from bottom.
152 | Return error if list is empty, otherwise next element or last.
153 |
154 |
drop(#reader{}) -> #reader{}.
155 |
Drops N elements starting from reader.
156 |
157 |
take(#reader{}) -> #reader{}.
158 |
Trying to consume N records from stream using its current value and direction.
159 | Returns consumed data. Usually you seek to some position and then consume some data.
160 |
161 |
append(tuple(), list()) -> term().
162 |
Adds record to feed.
163 |
164 |
remove(tuple(), list()) -> term().
165 |
Removes record from feed.
166 |
167 |
cut(list(), term()) -> #ok{} | #error{}.
168 |
Cuts the feed up to a given key.
169 |
170 |
171 |
172 |
This module may refer to:
173 | kvs,
174 | kvs_st.
175 |
