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Ability to advance replication slots
Ability to advance both physical and logical replication slots using a new user function pg_replication_slot_advance(). For logical advance that means records are consumed as fast as possible and changes are not given to output plugin for sending. Makes 2nd phase (after we reached SNAPBUILD_FULL_SNAPSHOT) of replication slot creation faster, especially when there are big transactions as the reorder buffer does not have to deal with data changes and does not have to spill to disk. Author: Petr Jelinek Reviewed-by: Simon Riggs
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10 files changed

+333
-17
lines changed

10 files changed

+333
-17
lines changed

‎contrib/test_decoding/expected/slot.out

Lines changed: 30 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -92,6 +92,36 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot2', NULL, NULL, 'in
9292
COMMIT
9393
(3 rows)
9494

95+
INSERT INTO replication_example(somedata, text) VALUES (1, 4);
96+
INSERT INTO replication_example(somedata, text) VALUES (1, 5);
97+
SELECT pg_current_wal_lsn() AS wal_lsn \gset
98+
INSERT INTO replication_example(somedata, text) VALUES (1, 6);
99+
SELECT end_lsn FROM pg_replication_slot_advance('regression_slot1', :'wal_lsn') \gset
100+
SELECT slot_name FROM pg_replication_slot_advance('regression_slot2', pg_current_wal_lsn());
101+
slot_name
102+
------------------
103+
regression_slot2
104+
(1 row)
105+
106+
SELECT :'wal_lsn' = :'end_lsn';
107+
?column?
108+
----------
109+
t
110+
(1 row)
111+
112+
SELECT data FROM pg_logical_slot_get_changes('regression_slot1', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
113+
data
114+
---------------------------------------------------------------------------------------------------------
115+
BEGIN
116+
table public.replication_example: INSERT: id[integer]:6 somedata[integer]:1 text[character varying]:'6'
117+
COMMIT
118+
(3 rows)
119+
120+
SELECT data FROM pg_logical_slot_get_changes('regression_slot2', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
121+
data
122+
------
123+
(0 rows)
124+
95125
DROP TABLE replication_example;
96126
-- error
97127
SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot1', 'test_decoding', true);

‎contrib/test_decoding/sql/slot.sql

Lines changed: 15 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -45,6 +45,21 @@ INSERT INTO replication_example(somedata, text) VALUES (1, 3);
4545
SELECT data FROM pg_logical_slot_get_changes('regression_slot1', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
4646
SELECT data FROM pg_logical_slot_get_changes('regression_slot2', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
4747

48+
INSERT INTO replication_example(somedata, text) VALUES (1, 4);
49+
INSERT INTO replication_example(somedata, text) VALUES (1, 5);
50+
51+
SELECT pg_current_wal_lsn() AS wal_lsn \gset
52+
53+
INSERT INTO replication_example(somedata, text) VALUES (1, 6);
54+
55+
SELECT end_lsn FROM pg_replication_slot_advance('regression_slot1', :'wal_lsn') \gset
56+
SELECT slot_name FROM pg_replication_slot_advance('regression_slot2', pg_current_wal_lsn());
57+
58+
SELECT :'wal_lsn' = :'end_lsn';
59+
60+
SELECT data FROM pg_logical_slot_get_changes('regression_slot1', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
61+
SELECT data FROM pg_logical_slot_get_changes('regression_slot2', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
62+
4863
DROP TABLE replication_example;
4964

5065
-- error

‎doc/src/sgml/func.sgml

Lines changed: 19 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -19155,6 +19155,25 @@ postgres=# SELECT * FROM pg_walfile_name_offset(pg_stop_backup());
1915519155
</entry>
1915619156
</row>
1915719157

19158+
<row>
19159+
<entry>
19160+
<indexterm>
19161+
<primary>pg_replication_slot_advance</primary>
19162+
</indexterm>
19163+
<literal><function>pg_replication_slot_advance(<parameter>slot_name</parameter> <type>name</type>, <parameter>upto_lsn</parameter> <type>pg_lsn</type>)</function></literal>
19164+
</entry>
19165+
<entry>
19166+
(<parameter>slot_name</parameter> <type>name</type>, <parameter>end_lsn</parameter> <type>pg_lsn</type>)
19167+
<type>bool</type>
19168+
</entry>
19169+
<entry>
19170+
Advances the current confirmed position of a replication slot named
19171+
<parameter>slot_name</parameter>. The slot will not be moved backwards,
19172+
and it will not be moved beyond the current insert location. Returns
19173+
name of the slot and real position to which it was advanced to.
19174+
</entry>
19175+
</row>
19176+
1915819177
<row>
1915919178
<entry id="pg-replication-origin-create">
1916019179
<indexterm>

‎src/backend/replication/logical/decode.c

Lines changed: 32 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -88,6 +88,9 @@ static void DecodeXLogTuple(char *data, Size len, ReorderBufferTupleBuf *tup);
8888
* call ReorderBufferProcessXid for each record type by default, because
8989
* e.g. empty xacts can be handled more efficiently if there's no previous
9090
* state for them.
91+
*
92+
* We also support the ability to fast forward thru records, skipping some
93+
* record types completely - see individual record types for details.
9194
*/
9295
void
9396
LogicalDecodingProcessRecord(LogicalDecodingContext *ctx, XLogReaderState *record)
@@ -332,8 +335,10 @@ DecodeStandbyOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
332335
xl_invalidations *invalidations =
333336
(xl_invalidations *) XLogRecGetData(r);
334337

335-
ReorderBufferImmediateInvalidation(
336-
ctx->reorder, invalidations->nmsgs, invalidations->msgs);
338+
if (!ctx->fast_forward)
339+
ReorderBufferImmediateInvalidation(ctx->reorder,
340+
invalidations->nmsgs,
341+
invalidations->msgs);
337342
}
338343
break;
339344
default:
@@ -353,14 +358,19 @@ DecodeHeap2Op(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
353358

354359
ReorderBufferProcessXid(ctx->reorder, xid, buf->origptr);
355360

356-
/* no point in doing anything yet */
357-
if (SnapBuildCurrentState(builder) < SNAPBUILD_FULL_SNAPSHOT)
361+
/*
362+
* If we don't have snapshot or we are just fast-forwarding, there is no
363+
* point in decoding changes.
364+
*/
365+
if (SnapBuildCurrentState(builder) < SNAPBUILD_FULL_SNAPSHOT ||
366+
ctx->fast_forward)
358367
return;
359368

360369
switch (info)
361370
{
362371
case XLOG_HEAP2_MULTI_INSERT:
363-
if (SnapBuildProcessChange(builder, xid, buf->origptr))
372+
if (!ctx->fast_forward &&
373+
SnapBuildProcessChange(builder, xid, buf->origptr))
364374
DecodeMultiInsert(ctx, buf);
365375
break;
366376
case XLOG_HEAP2_NEW_CID:
@@ -408,8 +418,12 @@ DecodeHeapOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
408418

409419
ReorderBufferProcessXid(ctx->reorder, xid, buf->origptr);
410420

411-
/* no point in doing anything yet */
412-
if (SnapBuildCurrentState(builder) < SNAPBUILD_FULL_SNAPSHOT)
421+
/*
422+
* If we don't have snapshot or we are just fast-forwarding, there is no
423+
* point in decoding data changes.
424+
*/
425+
if (SnapBuildCurrentState(builder) < SNAPBUILD_FULL_SNAPSHOT ||
426+
ctx->fast_forward)
413427
return;
414428

415429
switch (info)
@@ -501,8 +515,12 @@ DecodeLogicalMsgOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
501515

502516
ReorderBufferProcessXid(ctx->reorder, XLogRecGetXid(r), buf->origptr);
503517

504-
/* No point in doing anything yet. */
505-
if (SnapBuildCurrentState(builder) < SNAPBUILD_FULL_SNAPSHOT)
518+
/*
519+
* If we don't have snapshot or we are just fast-forwarding, there is no
520+
* point in decoding messages.
521+
*/
522+
if (SnapBuildCurrentState(builder) < SNAPBUILD_FULL_SNAPSHOT ||
523+
ctx->fast_forward)
506524
return;
507525

508526
message = (xl_logical_message *) XLogRecGetData(r);
@@ -554,8 +572,9 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
554572
*/
555573
if (parsed->nmsgs > 0)
556574
{
557-
ReorderBufferAddInvalidations(ctx->reorder, xid, buf->origptr,
558-
parsed->nmsgs, parsed->msgs);
575+
if (!ctx->fast_forward)
576+
ReorderBufferAddInvalidations(ctx->reorder, xid, buf->origptr,
577+
parsed->nmsgs, parsed->msgs);
559578
ReorderBufferXidSetCatalogChanges(ctx->reorder, xid, buf->origptr);
560579
}
561580

@@ -574,6 +593,7 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
574593
* are restarting or if we haven't assembled a consistent snapshot yet.
575594
* 2) The transaction happened in another database.
576595
* 3) The output plugin is not interested in the origin.
596+
* 4) We are doing fast-forwarding
577597
*
578598
* We can't just use ReorderBufferAbort() here, because we need to execute
579599
* the transaction's invalidations. This currently won't be needed if
@@ -589,7 +609,7 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
589609
*/
590610
if (SnapBuildXactNeedsSkip(ctx->snapshot_builder, buf->origptr) ||
591611
(parsed->dbId != InvalidOid && parsed->dbId != ctx->slot->data.database) ||
592-
FilterByOrigin(ctx, origin_id))
612+
ctx->fast_forward || FilterByOrigin(ctx, origin_id))
593613
{
594614
for (i = 0; i < parsed->nsubxacts; i++)
595615
{

‎src/backend/replication/logical/logical.c

Lines changed: 25 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -115,6 +115,7 @@ StartupDecodingContext(List *output_plugin_options,
115115
XLogRecPtr start_lsn,
116116
TransactionId xmin_horizon,
117117
bool need_full_snapshot,
118+
bool fast_forward,
118119
XLogPageReadCB read_page,
119120
LogicalOutputPluginWriterPrepareWrite prepare_write,
120121
LogicalOutputPluginWriterWrite do_write,
@@ -140,7 +141,8 @@ StartupDecodingContext(List *output_plugin_options,
140141
* (re-)load output plugins, so we detect a bad (removed) output plugin
141142
* now.
142143
*/
143-
LoadOutputPlugin(&ctx->callbacks, NameStr(slot->data.plugin));
144+
if (!fast_forward)
145+
LoadOutputPlugin(&ctx->callbacks, NameStr(slot->data.plugin));
144146

145147
/*
146148
* Now that the slot's xmin has been set, we can announce ourselves as a
@@ -191,6 +193,8 @@ StartupDecodingContext(List *output_plugin_options,
191193

192194
ctx->output_plugin_options = output_plugin_options;
193195

196+
ctx->fast_forward = fast_forward;
197+
194198
MemoryContextSwitchTo(old_context);
195199

196200
return ctx;
@@ -303,8 +307,9 @@ CreateInitDecodingContext(char *plugin,
303307
ReplicationSlotSave();
304308

305309
ctx = StartupDecodingContext(NIL, InvalidXLogRecPtr, xmin_horizon,
306-
need_full_snapshot, read_page, prepare_write,
307-
do_write, update_progress);
310+
need_full_snapshot, true,
311+
read_page, prepare_write, do_write,
312+
update_progress);
308313

309314
/* call output plugin initialization callback */
310315
old_context = MemoryContextSwitchTo(ctx->context);
@@ -342,6 +347,7 @@ CreateInitDecodingContext(char *plugin,
342347
LogicalDecodingContext *
343348
CreateDecodingContext(XLogRecPtr start_lsn,
344349
List *output_plugin_options,
350+
bool fast_forward,
345351
XLogPageReadCB read_page,
346352
LogicalOutputPluginWriterPrepareWrite prepare_write,
347353
LogicalOutputPluginWriterWrite do_write,
@@ -395,8 +401,8 @@ CreateDecodingContext(XLogRecPtr start_lsn,
395401

396402
ctx = StartupDecodingContext(output_plugin_options,
397403
start_lsn, InvalidTransactionId, false,
398-
read_page, prepare_write, do_write,
399-
update_progress);
404+
fast_forward, read_page, prepare_write,
405+
do_write, update_progress);
400406

401407
/* call output plugin initialization callback */
402408
old_context = MemoryContextSwitchTo(ctx->context);
@@ -573,6 +579,8 @@ startup_cb_wrapper(LogicalDecodingContext *ctx, OutputPluginOptions *opt, bool i
573579
LogicalErrorCallbackState state;
574580
ErrorContextCallback errcallback;
575581

582+
Assert(!ctx->fast_forward);
583+
576584
/* Push callback + info on the error context stack */
577585
state.ctx = ctx;
578586
state.callback_name = "startup";
@@ -598,6 +606,8 @@ shutdown_cb_wrapper(LogicalDecodingContext *ctx)
598606
LogicalErrorCallbackState state;
599607
ErrorContextCallback errcallback;
600608

609+
Assert(!ctx->fast_forward);
610+
601611
/* Push callback + info on the error context stack */
602612
state.ctx = ctx;
603613
state.callback_name = "shutdown";
@@ -629,6 +639,8 @@ begin_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn)
629639
LogicalErrorCallbackState state;
630640
ErrorContextCallback errcallback;
631641

642+
Assert(!ctx->fast_forward);
643+
632644
/* Push callback + info on the error context stack */
633645
state.ctx = ctx;
634646
state.callback_name = "begin";
@@ -658,6 +670,8 @@ commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
658670
LogicalErrorCallbackState state;
659671
ErrorContextCallback errcallback;
660672

673+
Assert(!ctx->fast_forward);
674+
661675
/* Push callback + info on the error context stack */
662676
state.ctx = ctx;
663677
state.callback_name = "commit";
@@ -687,6 +701,8 @@ change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
687701
LogicalErrorCallbackState state;
688702
ErrorContextCallback errcallback;
689703

704+
Assert(!ctx->fast_forward);
705+
690706
/* Push callback + info on the error context stack */
691707
state.ctx = ctx;
692708
state.callback_name = "change";
@@ -721,6 +737,8 @@ filter_by_origin_cb_wrapper(LogicalDecodingContext *ctx, RepOriginId origin_id)
721737
ErrorContextCallback errcallback;
722738
bool ret;
723739

740+
Assert(!ctx->fast_forward);
741+
724742
/* Push callback + info on the error context stack */
725743
state.ctx = ctx;
726744
state.callback_name = "filter_by_origin";
@@ -751,6 +769,8 @@ message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
751769
LogicalErrorCallbackState state;
752770
ErrorContextCallback errcallback;
753771

772+
Assert(!ctx->fast_forward);
773+
754774
if (ctx->callbacks.message_cb == NULL)
755775
return;
756776

‎src/backend/replication/logical/logicalfuncs.c

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -251,6 +251,7 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin
251251
/* restart at slot's confirmed_flush */
252252
ctx = CreateDecodingContext(InvalidXLogRecPtr,
253253
options,
254+
false,
254255
logical_read_local_xlog_page,
255256
LogicalOutputPrepareWrite,
256257
LogicalOutputWrite, NULL);

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