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Generic Messages for Logical Decoding

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API and mechanism to allow generic messages to be inserted into WAL that are
intended to be read by logical decoding plugins. This commit adds an optional
new callback to the logical decoding API.

Messages are either text or bytea. Messages can be transactional, or not, and
are identified by a prefix to allow multiple concurrent decoding plugins.

(Not to be confused with Generic WAL records, which are intended to allow crash
recovery of extensible objects.)

Author: Petr Jelinek and Andres Freund
Reviewers: Artur Zakirov, Tomas Vondra, Simon Riggs
Discussion: 5685F999.6010202@2ndquadrant.com
This commit is contained in:
Simon Riggs
2016-04-06 10:05:41 +01:00
parent 989be0810d
commit 3fe3511d05
27 changed files with 693 additions and 33 deletions
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18
contrib/test_decoding/test_decoding.c
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@ -21,6 +21,7 @@
#include "replication/output_plugin.h"
#include "replication/logical.h"
#include "replication/message.h"
#include "replication/origin.h"
#include "utils/builtins.h"
@ -63,6 +64,10 @@ static void pg_decode_change(LogicalDecodingContext *ctx,
ReorderBufferChange *change);
static bool pg_decode_filter(LogicalDecodingContext *ctx,
RepOriginId origin_id);
static void pg_decode_message(LogicalDecodingContext *ctx,
ReorderBufferTXN *txn, XLogRecPtr message_lsn,
bool transactional, const char *prefix,
Size sz, const char *message);
void
_PG_init(void)
@ -82,6 +87,7 @@ _PG_output_plugin_init(OutputPluginCallbacks *cb)
cb->commit_cb = pg_decode_commit_txn;
cb->filter_by_origin_cb = pg_decode_filter;
cb->shutdown_cb = pg_decode_shutdown;
cb->message_cb = pg_decode_message;
}
@ -471,3 +477,15 @@ pg_decode_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
OutputPluginWrite(ctx, true);
}
static void
pg_decode_message(LogicalDecodingContext *ctx,
ReorderBufferTXN *txn, XLogRecPtr lsn, bool transactional,
const char *prefix, Size sz, const char *message)
{
OutputPluginPrepareWrite(ctx, true);
appendStringInfo(ctx->out, "message: transactional: %d prefix: %s, sz: %zu content:",
transactional, prefix, sz);
appendBinaryStringInfo(ctx->out, message, sz);
OutputPluginWrite(ctx, true);
}