Uses old Rust 2015
0.0.7 |
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#182 in #change
1MB
26K
SLoC
JSONCDC
#jsoncdc on freenode irc
JSONCDC provides change data capture for Postgres, translating the Postgres write ahead log to JSON.
It is written in Rust and, being short, is a good skeleton project for other would be plugin authors who'd like to use Rust to write Postgres extensions.
Our library Requires rust stable 1.1 or greater.
Tasks to work on should be available on:
Copyright and License
Copyright (c) 2016 Alex Newman, Jason Dusek
JSONCDC is available under multiple licenses:
-
the same license as Postgres itself (
licenses/postgres
), -
the Apache 2.0 license (
licenses/apache
).
Status
JSONCDC is presently installable with pgxn
, from the unstable channel:
pgxn install jsoncdc --unstable
.
Usage
A basic demo:
SELECT * FROM pg_create_logical_replication_slot('jsoncdc', 'jsoncdc');
--- Wait for some transactions, and then:
SELECT * FROM pg_logical_slot_get_changes('jsoncdc', NULL, NULL);
The output format of jsoncdc
is very regular, consisting of begin
,
table
, insert
, update
and delete
clauses as JSON objects, one per line:
{ "begin": <xid> }
{ "table": <name of table>, "schema": <column names and type> }
...inserts, updates and deletes for this table...
{ "table": <name of next table>, "schema": <column names and type> }
...inserts, updates and deletes for next table...
{ "commit": <xid>, "t": <timestamp with timezone> }
With pg_recvlogical
and a little shell, you can leverage this very regular
formatting to get each transaction batched into a separate file:
pg_recvlogical -S jsoncdc -d postgres:/// --start -f - |
while read -r line
do
case "$line" in
'{ "begin": '*) # Close and reopen FD 9 for each new XID
fields=( $line )
xid="${fields[2]}"
exec 9>&-
exec 9> "txn-${xid}.json" ;;
esac
printf '%s\n' "$line" >&9 # Use printf because echo is non-portable
done
Formats
- JSON output
Features
- Monitored by Rust metrics