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Commit895a94d

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committed
Avoid incrementing the CommandCounter when CommandCounterIncrement is called
but no database changes have been made since the last CommandCounterIncrement.This should result in a significant improvement in the number of "commands"that can typically be performed within a transaction before hitting the 2^32CommandId size limit. In particular this buys back (and more) the possibleadverse consequences of my previous patch to fix plan caching behavior.The implementation requires tracking whether the current CommandCountervalue has been "used" to mark any tuples. CommandCounter values stored intosnapshots are presumed not to be used for this purpose. This requires somesmall executor changes, since the executor used to conflate the curcid ofthe snapshot it was using with the command ID to mark output tuples with.Separating these concepts allows some small simplifications in executor APIs.Something for the TODO list: look into having CommandCounterIncrement not doAcceptInvalidationMessages. It seems fairly bogus to be doing it there,but exactly where to do it instead isn't clear, and I'm disinclined to messwith asynchronous behavior during late beta.
1 parentf0f18c7 commit895a94d

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20 files changed

+217
-252
lines changed

20 files changed

+217
-252
lines changed

‎contrib/pgrowlocks/pgrowlocks.c‎

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
/*
2-
* $PostgreSQL: pgsql/contrib/pgrowlocks/pgrowlocks.c,v 1.7 2007/08/2822:59:30 tgl Exp $
2+
* $PostgreSQL: pgsql/contrib/pgrowlocks/pgrowlocks.c,v 1.8 2007/11/30 21:22:53 tgl Exp $
33
*
44
* Copyright (c) 2005-2006Tatsuo Ishii
55
*
@@ -117,8 +117,9 @@ pgrowlocks(PG_FUNCTION_ARGS)
117117
/* must hold a buffer lock to call HeapTupleSatisfiesUpdate */
118118
LockBuffer(scan->rs_cbuf,BUFFER_LOCK_SHARE);
119119

120-
if (HeapTupleSatisfiesUpdate(tuple->t_data,GetCurrentCommandId(),scan->rs_cbuf)
121-
==HeapTupleBeingUpdated)
120+
if (HeapTupleSatisfiesUpdate(tuple->t_data,
121+
GetCurrentCommandId(false),
122+
scan->rs_cbuf)==HeapTupleBeingUpdated)
122123
{
123124

124125
char**values;

‎src/backend/access/heap/heapam.c‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.245 2007/11/15 21:14:32 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.246 2007/11/30 21:22:53 tgl Exp $
1212
*
1313
*
1414
* INTERFACE ROUTINES
@@ -1891,7 +1891,7 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
18911891
Oid
18921892
simple_heap_insert(Relationrelation,HeapTupletup)
18931893
{
1894-
returnheap_insert(relation,tup,GetCurrentCommandId(), true, true);
1894+
returnheap_insert(relation,tup,GetCurrentCommandId(true), true, true);
18951895
}
18961896

18971897
/*
@@ -2174,7 +2174,7 @@ simple_heap_delete(Relation relation, ItemPointer tid)
21742174

21752175
result=heap_delete(relation,tid,
21762176
&update_ctid,&update_xmax,
2177-
GetCurrentCommandId(),InvalidSnapshot,
2177+
GetCurrentCommandId(true),InvalidSnapshot,
21782178
true/* wait for commit */ );
21792179
switch (result)
21802180
{
@@ -2817,7 +2817,7 @@ simple_heap_update(Relation relation, ItemPointer otid, HeapTuple tup)
28172817

28182818
result=heap_update(relation,otid,tup,
28192819
&update_ctid,&update_xmax,
2820-
GetCurrentCommandId(),InvalidSnapshot,
2820+
GetCurrentCommandId(true),InvalidSnapshot,
28212821
true/* wait for commit */ );
28222822
switch (result)
28232823
{

‎src/backend/access/heap/tuptoaster.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.79 2007/11/15 21:14:32 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.80 2007/11/30 21:22:53 tgl Exp $
1212
*
1313
*
1414
* INTERFACE ROUTINES
@@ -1086,7 +1086,7 @@ toast_save_datum(Relation rel, Datum value,
10861086
TupleDesctoasttupDesc;
10871087
Datumt_values[3];
10881088
boolt_isnull[3];
1089-
CommandIdmycid=GetCurrentCommandId();
1089+
CommandIdmycid=GetCurrentCommandId(true);
10901090
structvarlena*result;
10911091
structvaratt_externaltoast_pointer;
10921092
struct

‎src/backend/access/transam/xact.c‎

Lines changed: 51 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -10,7 +10,7 @@
1010
*
1111
*
1212
* IDENTIFICATION
13-
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.253 2007/11/15 21:14:32 momjian Exp $
13+
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.254 2007/11/30 21:22:53 tgl Exp $
1414
*
1515
*-------------------------------------------------------------------------
1616
*/
@@ -161,6 +161,7 @@ static TransactionState CurrentTransactionState = &TopTransactionStateData;
161161
*/
162162
staticSubTransactionIdcurrentSubTransactionId;
163163
staticCommandIdcurrentCommandId;
164+
staticboolcurrentCommandIdUsed;
164165

165166
/*
166167
* xactStartTimestamp is the value of transaction_timestamp().
@@ -435,11 +436,18 @@ GetCurrentSubTransactionId(void)
435436

436437
/*
437438
*GetCurrentCommandId
439+
*
440+
* "used" must be TRUE if the caller intends to use the command ID to mark
441+
* inserted/updated/deleted tuples. FALSE means the ID is being fetched
442+
* for read-only purposes (ie, as a snapshot validity cutoff). See
443+
* CommandCounterIncrement() for discussion.
438444
*/
439445
CommandId
440-
GetCurrentCommandId(void)
446+
GetCurrentCommandId(boolused)
441447
{
442448
/* this is global to a transaction, not subtransaction-local */
449+
if (used)
450+
currentCommandIdUsed= true;
443451
returncurrentCommandId;
444452
}
445453

@@ -566,25 +574,50 @@ TransactionIdIsCurrentTransactionId(TransactionId xid)
566574
void
567575
CommandCounterIncrement(void)
568576
{
569-
currentCommandId+=1;
570-
if (currentCommandId==FirstCommandId)/* check for overflow */
577+
/*
578+
* If the current value of the command counter hasn't been "used" to
579+
* mark tuples, we need not increment it, since there's no need to
580+
* distinguish a read-only command from others. This helps postpone
581+
* command counter overflow, and keeps no-op CommandCounterIncrement
582+
* operations cheap.
583+
*/
584+
if (currentCommandIdUsed)
571585
{
572-
currentCommandId-=1;
573-
ereport(ERROR,
574-
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
586+
currentCommandId+=1;
587+
if (currentCommandId==FirstCommandId)/* check for overflow */
588+
{
589+
currentCommandId-=1;
590+
ereport(ERROR,
591+
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
575592
errmsg("cannot have more than 2^32-1 commands in a transaction")));
576-
}
593+
}
594+
currentCommandIdUsed= false;
577595

578-
/* Propagate new command ID into static snapshots, if set */
579-
if (SerializableSnapshot)
580-
SerializableSnapshot->curcid=currentCommandId;
581-
if (LatestSnapshot)
582-
LatestSnapshot->curcid=currentCommandId;
596+
/* Propagate new command ID into static snapshots, if set */
597+
if (SerializableSnapshot)
598+
SerializableSnapshot->curcid=currentCommandId;
599+
if (LatestSnapshot)
600+
LatestSnapshot->curcid=currentCommandId;
601+
602+
/*
603+
* Make any catalog changes done by the just-completed command
604+
* visible in the local syscache. We obviously don't need to do
605+
* this after a read-only command. (But see hacks in inval.c
606+
* to make real sure we don't think a command that queued inval
607+
* messages was read-only.)
608+
*/
609+
AtCommit_LocalCache();
610+
}
583611

584612
/*
585-
* make cache changes visible to me.
613+
* Make any other backends' catalog changes visible to me.
614+
*
615+
* XXX this is probably in the wrong place: CommandCounterIncrement
616+
* should be purely a local operation, most likely. However fooling
617+
* with this will affect asynchronous cross-backend interactions,
618+
* which doesn't seem like a wise thing to do in late beta, so save
619+
* improving this for another day - tgl 2007-11-30
586620
*/
587-
AtCommit_LocalCache();
588621
AtStart_Cache();
589622
}
590623

@@ -1416,6 +1449,7 @@ StartTransaction(void)
14161449
s->subTransactionId=TopSubTransactionId;
14171450
currentSubTransactionId=TopSubTransactionId;
14181451
currentCommandId=FirstCommandId;
1452+
currentCommandIdUsed= false;
14191453

14201454
/*
14211455
* must initialize resource-management stuff first
@@ -4007,13 +4041,14 @@ ShowTransactionStateRec(TransactionState s)
40074041

40084042
/* use ereport to suppress computation if msg will not be printed */
40094043
ereport(DEBUG3,
4010-
(errmsg_internal("name: %s; blockState: %13s; state: %7s, xid/subid/cid: %u/%u/%u, nestlvl: %d, children: %s",
4044+
(errmsg_internal("name: %s; blockState: %13s; state: %7s, xid/subid/cid: %u/%u/%u%s, nestlvl: %d, children: %s",
40114045
PointerIsValid(s->name) ?s->name :"unnamed",
40124046
BlockStateAsString(s->blockState),
40134047
TransStateAsString(s->state),
40144048
(unsignedint)s->transactionId,
40154049
(unsignedint)s->subTransactionId,
40164050
(unsignedint)currentCommandId,
4051+
currentCommandIdUsed ?" (used)" :"",
40174052
s->nestingLevel,
40184053
nodeToString(s->childXids))));
40194054
}

‎src/backend/commands/async.c‎

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
99
* IDENTIFICATION
10-
* $PostgreSQL: pgsql/src/backend/commands/async.c,v 1.136 2007/04/12 06:53:46 neilc Exp $
10+
* $PostgreSQL: pgsql/src/backend/commands/async.c,v 1.137 2007/11/30 21:22:53 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -562,7 +562,8 @@ AtCommit_Notify(void)
562562
*/
563563
result=heap_update(lRel,&lTuple->t_self,rTuple,
564564
&update_ctid,&update_xmax,
565-
GetCurrentCommandId(),InvalidSnapshot,
565+
GetCurrentCommandId(true),
566+
InvalidSnapshot,
566567
false/* no wait for commit */ );
567568
switch (result)
568569
{

‎src/backend/commands/copy.c‎

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/commands/copy.c,v 1.288 2007/11/15 21:14:33 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/commands/copy.c,v 1.289 2007/11/30 21:22:53 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -1033,7 +1033,7 @@ DoCopy(const CopyStmt *stmt, const char *queryString)
10331033
* which COPY can be invoked, I think it's OK, because the active
10341034
* snapshot shouldn't be shared with anything else anyway.)
10351035
*/
1036-
ActiveSnapshot->curcid=GetCurrentCommandId();
1036+
ActiveSnapshot->curcid=GetCurrentCommandId(false);
10371037

10381038
/* Create dest receiver for COPY OUT */
10391039
dest=CreateDestReceiver(DestCopyOut,NULL);
@@ -1637,7 +1637,7 @@ CopyFrom(CopyState cstate)
16371637
ExprContext*econtext;/* used for ExecEvalExpr for default atts */
16381638
MemoryContextoldcontext=CurrentMemoryContext;
16391639
ErrorContextCallbackerrcontext;
1640-
CommandIdmycid=GetCurrentCommandId();
1640+
CommandIdmycid=GetCurrentCommandId(true);
16411641
booluse_wal= true;/* by default, use WAL logging */
16421642
booluse_fsm= true;/* by default, use FSM for free space */
16431643

‎src/backend/commands/explain.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1994-5, Regents of the University of California
88
*
99
* IDENTIFICATION
10-
* $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.167 2007/11/1522:25:15 momjian Exp $
10+
* $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.168 2007/11/30 21:22:54 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -233,7 +233,7 @@ ExplainOnePlan(PlannedStmt *plannedstmt, ParamListInfo params,
233233
* EXPLAIN can be invoked, I think it's OK, because the active snapshot
234234
* shouldn't be shared with anything else anyway.)
235235
*/
236-
ActiveSnapshot->curcid=GetCurrentCommandId();
236+
ActiveSnapshot->curcid=GetCurrentCommandId(false);
237237

238238
/* Create a QueryDesc requesting no output */
239239
queryDesc=CreateQueryDesc(plannedstmt,

‎src/backend/commands/trigger.c‎

Lines changed: 11 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
99
* IDENTIFICATION
10-
* $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.224 2007/11/16 01:51:22 momjian Exp $
10+
* $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.225 2007/11/30 21:22:54 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -51,7 +51,6 @@ static void InsertTrigger(TriggerDesc *trigdesc, Trigger *trigger, int indx);
5151
staticHeapTupleGetTupleForTrigger(EState*estate,
5252
ResultRelInfo*relinfo,
5353
ItemPointertid,
54-
CommandIdcid,
5554
TupleTableSlot**newSlot);
5655
staticHeapTupleExecCallTriggerFunc(TriggerData*trigdata,
5756
inttgindx,
@@ -1801,8 +1800,7 @@ ExecASDeleteTriggers(EState *estate, ResultRelInfo *relinfo)
18011800

18021801
bool
18031802
ExecBRDeleteTriggers(EState*estate,ResultRelInfo*relinfo,
1804-
ItemPointertupleid,
1805-
CommandIdcid)
1803+
ItemPointertupleid)
18061804
{
18071805
TriggerDesc*trigdesc=relinfo->ri_TrigDesc;
18081806
intntrigs=trigdesc->n_before_row[TRIGGER_EVENT_DELETE];
@@ -1814,7 +1812,7 @@ ExecBRDeleteTriggers(EState *estate, ResultRelInfo *relinfo,
18141812
TupleTableSlot*newSlot;
18151813
inti;
18161814

1817-
trigtuple=GetTupleForTrigger(estate,relinfo,tupleid,cid,&newSlot);
1815+
trigtuple=GetTupleForTrigger(estate,relinfo,tupleid,&newSlot);
18181816
if (trigtuple==NULL)
18191817
return false;
18201818

@@ -1871,9 +1869,7 @@ ExecARDeleteTriggers(EState *estate, ResultRelInfo *relinfo,
18711869
if (trigdesc&&trigdesc->n_after_row[TRIGGER_EVENT_DELETE]>0)
18721870
{
18731871
HeapTupletrigtuple=GetTupleForTrigger(estate,relinfo,
1874-
tupleid,
1875-
(CommandId)0,
1876-
NULL);
1872+
tupleid,NULL);
18771873

18781874
AfterTriggerSaveEvent(relinfo,TRIGGER_EVENT_DELETE,
18791875
true,trigtuple,NULL);
@@ -1952,8 +1948,7 @@ ExecASUpdateTriggers(EState *estate, ResultRelInfo *relinfo)
19521948

19531949
HeapTuple
19541950
ExecBRUpdateTriggers(EState*estate,ResultRelInfo*relinfo,
1955-
ItemPointertupleid,HeapTuplenewtuple,
1956-
CommandIdcid)
1951+
ItemPointertupleid,HeapTuplenewtuple)
19571952
{
19581953
TriggerDesc*trigdesc=relinfo->ri_TrigDesc;
19591954
intntrigs=trigdesc->n_before_row[TRIGGER_EVENT_UPDATE];
@@ -1965,7 +1960,7 @@ ExecBRUpdateTriggers(EState *estate, ResultRelInfo *relinfo,
19651960
TupleTableSlot*newSlot;
19661961
inti;
19671962

1968-
trigtuple=GetTupleForTrigger(estate,relinfo,tupleid,cid,&newSlot);
1963+
trigtuple=GetTupleForTrigger(estate,relinfo,tupleid,&newSlot);
19691964
if (trigtuple==NULL)
19701965
returnNULL;
19711966

@@ -2025,9 +2020,7 @@ ExecARUpdateTriggers(EState *estate, ResultRelInfo *relinfo,
20252020
if (trigdesc&&trigdesc->n_after_row[TRIGGER_EVENT_UPDATE]>0)
20262021
{
20272022
HeapTupletrigtuple=GetTupleForTrigger(estate,relinfo,
2028-
tupleid,
2029-
(CommandId)0,
2030-
NULL);
2023+
tupleid,NULL);
20312024

20322025
AfterTriggerSaveEvent(relinfo,TRIGGER_EVENT_UPDATE,
20332026
true,trigtuple,newtuple);
@@ -2038,7 +2031,7 @@ ExecARUpdateTriggers(EState *estate, ResultRelInfo *relinfo,
20382031

20392032
staticHeapTuple
20402033
GetTupleForTrigger(EState*estate,ResultRelInfo*relinfo,
2041-
ItemPointertid,CommandIdcid,
2034+
ItemPointertid,
20422035
TupleTableSlot**newSlot)
20432036
{
20442037
Relationrelation=relinfo->ri_RelationDesc;
@@ -2060,7 +2053,8 @@ GetTupleForTrigger(EState *estate, ResultRelInfo *relinfo,
20602053
ltrmark:;
20612054
tuple.t_self=*tid;
20622055
test=heap_lock_tuple(relation,&tuple,&buffer,
2063-
&update_ctid,&update_xmax,cid,
2056+
&update_ctid,&update_xmax,
2057+
estate->es_output_cid,
20642058
LockTupleExclusive, false);
20652059
switch (test)
20662060
{
@@ -2086,8 +2080,7 @@ ltrmark:;
20862080
epqslot=EvalPlanQual(estate,
20872081
relinfo->ri_RangeTableIndex,
20882082
&update_ctid,
2089-
update_xmax,
2090-
cid);
2083+
update_xmax);
20912084
if (!TupIsNull(epqslot))
20922085
{
20932086
*tid=update_ctid;

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