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When implementing a replication solution ontop of logical decoding, two
related problems exist:
* How to safely keep track of replication progress
* How to change replication behavior, based on the origin of a row;
e.g. to avoid loops in bi-directional replication setups
The solution to these problems, as implemented here, consist out of
three parts:
1) 'replication origins', which identify nodes in a replication setup.
2) 'replication progress tracking', which remembers, for each
replication origin, how far replay has progressed in a efficient and
crash safe manner.
3) The ability to filter out changes performed on the behest of a
replication origin during logical decoding; this allows complex
replication topologies. E.g. by filtering all replayed changes out.
Most of this could also be implemented in "userspace", e.g. by inserting
additional rows contain origin information, but that ends up being much
less efficient and more complicated. We don't want to require various
replication solutions to reimplement logic for this independently. The
infrastructure is intended to be generic enough to be reusable.
This infrastructure also replaces the 'nodeid' infrastructure of commit
timestamps. It is intended to provide all the former capabilities,
except that there's only 2^16 different origins; but now they integrate
with logical decoding. Additionally more functionality is accessible via
SQL. Since the commit timestamp infrastructure has also been introduced
in 9.5 (commit 73c986add
) changing the API is not a problem.
For now the number of origins for which the replication progress can be
tracked simultaneously is determined by the max_replication_slots
GUC. That GUC is not a perfect match to configure this, but there
doesn't seem to be sufficient reason to introduce a separate new one.
Bumps both catversion and wal page magic.
Author: Andres Freund, with contributions from Petr Jelinek and Craig Ringer
Reviewed-By: Heikki Linnakangas, Petr Jelinek, Robert Haas, Steve Singer
Discussion: 20150216002155.GI15326@awork2.anarazel.de,
20140923182422.GA15776@alap3.anarazel.de,
20131114172632.GE7522@alap2.anarazel.de
474 lines
12 KiB
C
474 lines
12 KiB
C
/*-------------------------------------------------------------------------
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*
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* test_decoding.c
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* example logical decoding output plugin
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*
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* Copyright (c) 2012-2015, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* contrib/test_decoding/test_decoding.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/sysattr.h"
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#include "catalog/pg_class.h"
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#include "catalog/pg_type.h"
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#include "nodes/parsenodes.h"
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#include "replication/output_plugin.h"
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#include "replication/logical.h"
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#include "replication/origin.h"
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#include "utils/builtins.h"
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#include "utils/lsyscache.h"
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#include "utils/memutils.h"
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#include "utils/rel.h"
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#include "utils/relcache.h"
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#include "utils/syscache.h"
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#include "utils/typcache.h"
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PG_MODULE_MAGIC;
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/* These must be available to pg_dlsym() */
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extern void _PG_init(void);
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extern void _PG_output_plugin_init(OutputPluginCallbacks *cb);
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typedef struct
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{
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MemoryContext context;
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bool include_xids;
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bool include_timestamp;
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bool skip_empty_xacts;
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bool xact_wrote_changes;
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bool only_local;
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} TestDecodingData;
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static void pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
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bool is_init);
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static void pg_decode_shutdown(LogicalDecodingContext *ctx);
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static void pg_decode_begin_txn(LogicalDecodingContext *ctx,
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ReorderBufferTXN *txn);
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static void pg_output_begin(LogicalDecodingContext *ctx,
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TestDecodingData *data,
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ReorderBufferTXN *txn,
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bool last_write);
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static void pg_decode_commit_txn(LogicalDecodingContext *ctx,
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ReorderBufferTXN *txn, XLogRecPtr commit_lsn);
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static void pg_decode_change(LogicalDecodingContext *ctx,
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ReorderBufferTXN *txn, Relation rel,
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ReorderBufferChange *change);
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static bool pg_decode_filter(LogicalDecodingContext *ctx,
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RepOriginId origin_id);
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void
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_PG_init(void)
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{
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/* other plugins can perform things here */
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}
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/* specify output plugin callbacks */
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void
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_PG_output_plugin_init(OutputPluginCallbacks *cb)
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{
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AssertVariableIsOfType(&_PG_output_plugin_init, LogicalOutputPluginInit);
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cb->startup_cb = pg_decode_startup;
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cb->begin_cb = pg_decode_begin_txn;
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cb->change_cb = pg_decode_change;
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cb->commit_cb = pg_decode_commit_txn;
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cb->filter_by_origin_cb = pg_decode_filter;
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cb->shutdown_cb = pg_decode_shutdown;
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}
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/* initialize this plugin */
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static void
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pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
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bool is_init)
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{
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ListCell *option;
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TestDecodingData *data;
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data = palloc0(sizeof(TestDecodingData));
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data->context = AllocSetContextCreate(ctx->context,
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"text conversion context",
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ALLOCSET_DEFAULT_MINSIZE,
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ALLOCSET_DEFAULT_INITSIZE,
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ALLOCSET_DEFAULT_MAXSIZE);
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data->include_xids = true;
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data->include_timestamp = false;
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data->skip_empty_xacts = false;
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data->only_local = false;
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ctx->output_plugin_private = data;
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opt->output_type = OUTPUT_PLUGIN_TEXTUAL_OUTPUT;
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foreach(option, ctx->output_plugin_options)
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{
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DefElem *elem = lfirst(option);
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Assert(elem->arg == NULL || IsA(elem->arg, String));
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if (strcmp(elem->defname, "include-xids") == 0)
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{
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/* if option does not provide a value, it means its value is true */
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if (elem->arg == NULL)
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data->include_xids = true;
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else if (!parse_bool(strVal(elem->arg), &data->include_xids))
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ereport(ERROR,
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(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
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errmsg("could not parse value \"%s\" for parameter \"%s\"",
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strVal(elem->arg), elem->defname)));
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}
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else if (strcmp(elem->defname, "include-timestamp") == 0)
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{
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if (elem->arg == NULL)
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data->include_timestamp = true;
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else if (!parse_bool(strVal(elem->arg), &data->include_timestamp))
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ereport(ERROR,
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(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
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errmsg("could not parse value \"%s\" for parameter \"%s\"",
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strVal(elem->arg), elem->defname)));
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}
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else if (strcmp(elem->defname, "force-binary") == 0)
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{
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bool force_binary;
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if (elem->arg == NULL)
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continue;
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else if (!parse_bool(strVal(elem->arg), &force_binary))
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ereport(ERROR,
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(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
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errmsg("could not parse value \"%s\" for parameter \"%s\"",
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strVal(elem->arg), elem->defname)));
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if (force_binary)
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opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT;
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}
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else if (strcmp(elem->defname, "skip-empty-xacts") == 0)
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{
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if (elem->arg == NULL)
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data->skip_empty_xacts = true;
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else if (!parse_bool(strVal(elem->arg), &data->skip_empty_xacts))
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ereport(ERROR,
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(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
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errmsg("could not parse value \"%s\" for parameter \"%s\"",
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strVal(elem->arg), elem->defname)));
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}
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else if (strcmp(elem->defname, "only-local") == 0)
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{
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if (elem->arg == NULL)
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data->only_local = true;
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else if (!parse_bool(strVal(elem->arg), &data->only_local))
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ereport(ERROR,
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(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
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errmsg("could not parse value \"%s\" for parameter \"%s\"",
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strVal(elem->arg), elem->defname)));
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}
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else
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{
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ereport(ERROR,
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(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
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errmsg("option \"%s\" = \"%s\" is unknown",
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elem->defname,
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elem->arg ? strVal(elem->arg) : "(null)")));
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}
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}
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}
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/* cleanup this plugin's resources */
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static void
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pg_decode_shutdown(LogicalDecodingContext *ctx)
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{
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TestDecodingData *data = ctx->output_plugin_private;
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/* cleanup our own resources via memory context reset */
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MemoryContextDelete(data->context);
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}
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/* BEGIN callback */
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static void
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pg_decode_begin_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn)
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{
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TestDecodingData *data = ctx->output_plugin_private;
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data->xact_wrote_changes = false;
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if (data->skip_empty_xacts)
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return;
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pg_output_begin(ctx, data, txn, true);
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}
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static void
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pg_output_begin(LogicalDecodingContext *ctx, TestDecodingData *data, ReorderBufferTXN *txn, bool last_write)
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{
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OutputPluginPrepareWrite(ctx, last_write);
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if (data->include_xids)
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appendStringInfo(ctx->out, "BEGIN %u", txn->xid);
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else
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appendStringInfoString(ctx->out, "BEGIN");
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OutputPluginWrite(ctx, last_write);
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}
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/* COMMIT callback */
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static void
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pg_decode_commit_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
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XLogRecPtr commit_lsn)
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{
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TestDecodingData *data = ctx->output_plugin_private;
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if (data->skip_empty_xacts && !data->xact_wrote_changes)
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return;
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OutputPluginPrepareWrite(ctx, true);
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if (data->include_xids)
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appendStringInfo(ctx->out, "COMMIT %u", txn->xid);
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else
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appendStringInfoString(ctx->out, "COMMIT");
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if (data->include_timestamp)
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appendStringInfo(ctx->out, " (at %s)",
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timestamptz_to_str(txn->commit_time));
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OutputPluginWrite(ctx, true);
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}
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static bool
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pg_decode_filter(LogicalDecodingContext *ctx,
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RepOriginId origin_id)
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{
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TestDecodingData *data = ctx->output_plugin_private;
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if (data->only_local && origin_id != InvalidRepOriginId)
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return true;
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return false;
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}
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/*
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* Print literal `outputstr' already represented as string of type `typid'
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* into stringbuf `s'.
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*
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* Some builtin types aren't quoted, the rest is quoted. Escaping is done as
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* if standard_conforming_strings were enabled.
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*/
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static void
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print_literal(StringInfo s, Oid typid, char *outputstr)
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{
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const char *valptr;
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switch (typid)
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{
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case INT2OID:
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case INT4OID:
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case INT8OID:
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case OIDOID:
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case FLOAT4OID:
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case FLOAT8OID:
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case NUMERICOID:
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/* NB: We don't care about Inf, NaN et al. */
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appendStringInfoString(s, outputstr);
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break;
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case BITOID:
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case VARBITOID:
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appendStringInfo(s, "B'%s'", outputstr);
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break;
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case BOOLOID:
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if (strcmp(outputstr, "t") == 0)
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appendStringInfoString(s, "true");
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else
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appendStringInfoString(s, "false");
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break;
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default:
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appendStringInfoChar(s, '\'');
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for (valptr = outputstr; *valptr; valptr++)
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{
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char ch = *valptr;
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if (SQL_STR_DOUBLE(ch, false))
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appendStringInfoChar(s, ch);
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appendStringInfoChar(s, ch);
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}
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appendStringInfoChar(s, '\'');
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break;
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}
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}
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/* print the tuple 'tuple' into the StringInfo s */
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static void
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tuple_to_stringinfo(StringInfo s, TupleDesc tupdesc, HeapTuple tuple, bool skip_nulls)
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{
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int natt;
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Oid oid;
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/* print oid of tuple, it's not included in the TupleDesc */
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if ((oid = HeapTupleHeaderGetOid(tuple->t_data)) != InvalidOid)
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{
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appendStringInfo(s, " oid[oid]:%u", oid);
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}
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/* print all columns individually */
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for (natt = 0; natt < tupdesc->natts; natt++)
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{
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Form_pg_attribute attr; /* the attribute itself */
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Oid typid; /* type of current attribute */
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Oid typoutput; /* output function */
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bool typisvarlena;
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Datum origval; /* possibly toasted Datum */
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bool isnull; /* column is null? */
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attr = tupdesc->attrs[natt];
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/*
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* don't print dropped columns, we can't be sure everything is
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* available for them
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*/
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if (attr->attisdropped)
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continue;
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/*
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* Don't print system columns, oid will already have been printed if
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* present.
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*/
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if (attr->attnum < 0)
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continue;
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typid = attr->atttypid;
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/* get Datum from tuple */
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origval = fastgetattr(tuple, natt + 1, tupdesc, &isnull);
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if (isnull && skip_nulls)
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continue;
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/* print attribute name */
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appendStringInfoChar(s, ' ');
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appendStringInfoString(s, quote_identifier(NameStr(attr->attname)));
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/* print attribute type */
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appendStringInfoChar(s, '[');
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appendStringInfoString(s, format_type_be(typid));
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appendStringInfoChar(s, ']');
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/* query output function */
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getTypeOutputInfo(typid,
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&typoutput, &typisvarlena);
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/* print separator */
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appendStringInfoChar(s, ':');
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/* print data */
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if (isnull)
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appendStringInfoString(s, "null");
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else if (typisvarlena && VARATT_IS_EXTERNAL_ONDISK(origval))
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appendStringInfoString(s, "unchanged-toast-datum");
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else if (!typisvarlena)
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print_literal(s, typid,
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OidOutputFunctionCall(typoutput, origval));
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else
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{
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Datum val; /* definitely detoasted Datum */
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val = PointerGetDatum(PG_DETOAST_DATUM(origval));
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print_literal(s, typid, OidOutputFunctionCall(typoutput, val));
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}
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}
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}
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/*
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* callback for individual changed tuples
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*/
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static void
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pg_decode_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
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Relation relation, ReorderBufferChange *change)
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{
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TestDecodingData *data;
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Form_pg_class class_form;
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TupleDesc tupdesc;
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MemoryContext old;
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data = ctx->output_plugin_private;
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/* output BEGIN if we haven't yet */
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if (data->skip_empty_xacts && !data->xact_wrote_changes)
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{
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pg_output_begin(ctx, data, txn, false);
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}
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data->xact_wrote_changes = true;
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class_form = RelationGetForm(relation);
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tupdesc = RelationGetDescr(relation);
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/* Avoid leaking memory by using and resetting our own context */
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old = MemoryContextSwitchTo(data->context);
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OutputPluginPrepareWrite(ctx, true);
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appendStringInfoString(ctx->out, "table ");
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appendStringInfoString(ctx->out,
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quote_qualified_identifier(
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get_namespace_name(
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get_rel_namespace(RelationGetRelid(relation))),
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NameStr(class_form->relname)));
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appendStringInfoString(ctx->out, ":");
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switch (change->action)
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{
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case REORDER_BUFFER_CHANGE_INSERT:
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appendStringInfoString(ctx->out, " INSERT:");
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if (change->data.tp.newtuple == NULL)
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appendStringInfoString(ctx->out, " (no-tuple-data)");
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else
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tuple_to_stringinfo(ctx->out, tupdesc,
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&change->data.tp.newtuple->tuple,
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false);
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break;
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case REORDER_BUFFER_CHANGE_UPDATE:
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appendStringInfoString(ctx->out, " UPDATE:");
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if (change->data.tp.oldtuple != NULL)
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{
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appendStringInfoString(ctx->out, " old-key:");
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tuple_to_stringinfo(ctx->out, tupdesc,
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&change->data.tp.oldtuple->tuple,
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true);
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appendStringInfoString(ctx->out, " new-tuple:");
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}
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if (change->data.tp.newtuple == NULL)
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appendStringInfoString(ctx->out, " (no-tuple-data)");
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else
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tuple_to_stringinfo(ctx->out, tupdesc,
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&change->data.tp.newtuple->tuple,
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false);
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break;
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case REORDER_BUFFER_CHANGE_DELETE:
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appendStringInfoString(ctx->out, " DELETE:");
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/* if there was no PK, we only know that a delete happened */
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if (change->data.tp.oldtuple == NULL)
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appendStringInfoString(ctx->out, " (no-tuple-data)");
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/* In DELETE, only the replica identity is present; display that */
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else
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tuple_to_stringinfo(ctx->out, tupdesc,
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&change->data.tp.oldtuple->tuple,
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true);
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break;
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default:
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Assert(false);
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}
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MemoryContextSwitchTo(old);
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MemoryContextReset(data->context);
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OutputPluginWrite(ctx, true);
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}
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