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Commit4d86ae4

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For multi-table ANALYZE, use per-table transactions when possible
(ie, when not inside a transaction block), so that we can avoid holdinglocks longer than necessary. Per trouble report from Philip Warner.
1 parente26c403 commit4d86ae4

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3 files changed

+124
-67
lines changed

3 files changed

+124
-67
lines changed

‎src/backend/access/transam/xact.c

Lines changed: 32 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/transam/xact.c,v 1.166 2004/05/21 05:07:56 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.167 2004/05/22 23:14:37 tgl Exp $
1212
*
1313
* NOTES
1414
*Transaction aborts can now occur two ways:
@@ -1417,7 +1417,7 @@ PreventTransactionChain(void *stmtNode, const char *stmtType)
14171417
errmsg("%s cannot be executed from a function",stmtType)));
14181418
/* If we got past IsTransactionBlock test, should be in default state */
14191419
if (CurrentTransactionState->blockState!=TBLOCK_DEFAULT&&
1420-
CurrentTransactionState->blockState!=TBLOCK_STARTED)
1420+
CurrentTransactionState->blockState!=TBLOCK_STARTED)
14211421
elog(ERROR,"cannot prevent transaction chain");
14221422
/* all okay */
14231423
}
@@ -1462,6 +1462,36 @@ RequireTransactionChain(void *stmtNode, const char *stmtType)
14621462
stmtType)));
14631463
}
14641464

1465+
/*
1466+
*IsInTransactionChain
1467+
*
1468+
*This routine is for statements that need to behave differently inside
1469+
*a transaction block than when running as single commands. ANALYZE is
1470+
*currently the only example.
1471+
*
1472+
*stmtNode: pointer to parameter block for statement; this is used in
1473+
*a very klugy way to determine whether we are inside a function.
1474+
*/
1475+
bool
1476+
IsInTransactionChain(void*stmtNode)
1477+
{
1478+
/*
1479+
* Return true on same conditions that would make PreventTransactionChain
1480+
* error out
1481+
*/
1482+
if (IsTransactionBlock())
1483+
return true;
1484+
1485+
if (!MemoryContextContains(QueryContext,stmtNode))
1486+
return true;
1487+
1488+
if (CurrentTransactionState->blockState!=TBLOCK_DEFAULT&&
1489+
CurrentTransactionState->blockState!=TBLOCK_STARTED)
1490+
return true;
1491+
1492+
return false;
1493+
}
1494+
14651495

14661496
/*
14671497
* Register or deregister callback functions for end-of-xact cleanup

‎src/backend/commands/vacuum.c

Lines changed: 90 additions & 64 deletions
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,7 @@
1313
*
1414
*
1515
* IDENTIFICATION
16-
* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.276 2004/05/21 16:08:46 tgl Exp $
16+
* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.277 2004/05/22 23:14:38 tgl Exp $
1717
*
1818
*-------------------------------------------------------------------------
1919
*/
@@ -161,7 +161,9 @@ vacuum(VacuumStmt *vacstmt)
161161
MemoryContextanl_context=NULL;
162162
TransactionIdinitialOldestXmin=InvalidTransactionId;
163163
TransactionIdinitialFreezeLimit=InvalidTransactionId;
164-
boolall_rels;
164+
boolall_rels,
165+
in_outer_xact,
166+
use_own_xacts;
165167
List*relations,
166168
*cur;
167169

@@ -177,10 +179,23 @@ vacuum(VacuumStmt *vacstmt)
177179
* Furthermore, the forced commit that occurs before truncating the
178180
* relation's file would have the effect of committing the rest of the
179181
* user's transaction too, which would certainly not be the desired
180-
* behavior.
182+
* behavior. (This only applies to VACUUM FULL, though. We could
183+
* in theory run lazy VACUUM inside a transaction block, but we choose
184+
* to disallow that case because we'd rather commit as soon as possible
185+
* after finishing the vacuum. This is mainly so that we can let go the
186+
* AccessExclusiveLock that we may be holding.)
187+
*
188+
* ANALYZE (without VACUUM) can run either way.
181189
*/
182190
if (vacstmt->vacuum)
191+
{
183192
PreventTransactionChain((void*)vacstmt,stmttype);
193+
in_outer_xact= false;
194+
}
195+
else
196+
{
197+
in_outer_xact=IsInTransactionChain((void*)vacstmt);
198+
}
184199

185200
/* Turn vacuum cost accounting on or off */
186201
VacuumCostActive= (VacuumCostNaptime>0);
@@ -205,81 +220,89 @@ vacuum(VacuumStmt *vacstmt)
205220
ALLOCSET_DEFAULT_INITSIZE,
206221
ALLOCSET_DEFAULT_MAXSIZE);
207222

208-
/*
209-
* If we are running only ANALYZE, we don't need per-table
210-
* transactions, but we still need a memory context with table
211-
* lifetime.
212-
*/
213-
if (vacstmt->analyze&& !vacstmt->vacuum)
214-
anl_context=AllocSetContextCreate(PortalContext,
215-
"Analyze",
216-
ALLOCSET_DEFAULT_MINSIZE,
217-
ALLOCSET_DEFAULT_INITSIZE,
218-
ALLOCSET_DEFAULT_MAXSIZE);
219-
220223
/* Assume we are processing everything unless one table is mentioned */
221224
all_rels= (vacstmt->relation==NULL);
222225

223226
/* Build list of relations to process (note this lives in vac_context) */
224227
relations=get_rel_oids(vacstmt->relation,stmttype);
225228

229+
if (vacstmt->vacuum&&all_rels)
230+
{
231+
/*
232+
* It's a database-wide VACUUM.
233+
*
234+
* Compute the initially applicable OldestXmin and FreezeLimit
235+
* XIDs, so that we can record these values at the end of the
236+
* VACUUM. Note that individual tables may well be processed
237+
* with newer values, but we can guarantee that no
238+
* (non-shared) relations are processed with older ones.
239+
*
240+
* It is okay to record non-shared values in pg_database, even
241+
* though we may vacuum shared relations with older cutoffs,
242+
* because only the minimum of the values present in
243+
* pg_database matters. We can be sure that shared relations
244+
* have at some time been vacuumed with cutoffs no worse than
245+
* the global minimum; for, if there is a backend in some
246+
* other DB with xmin = OLDXMIN that's determining the cutoff
247+
* with which we vacuum shared relations, it is not possible
248+
* for that database to have a cutoff newer than OLDXMIN
249+
* recorded in pg_database.
250+
*/
251+
vacuum_set_xid_limits(vacstmt, false,
252+
&initialOldestXmin,
253+
&initialFreezeLimit);
254+
}
255+
226256
/*
227-
* Formerly, there was code here to prevent more than one VACUUM from
228-
* executing concurrently in the same database. However, there's no
229-
* good reason to prevent that, and manually removing lockfiles after
230-
* a vacuum crash was a pain for dbadmins.So, forget about
231-
* lockfiles, and just rely on the locks we grab on each target table
232-
* to ensure that there aren't two VACUUMs running on the same table
233-
* at the same time.
257+
* Decide whether we need to start/commit our own transactions.
258+
*
259+
* For VACUUM (with or without ANALYZE): always do so, so that we
260+
* can release locks as soon as possible. (We could possibly use the
261+
* outer transaction for a one-table VACUUM, but handling TOAST tables
262+
* would be problematic.)
263+
*
264+
* For ANALYZE (no VACUUM): if inside a transaction block, we cannot
265+
* start/commit our own transactions. Also, there's no need to do so
266+
* if only processing one relation. For multiple relations when not
267+
* within a transaction block, use own transactions so we can release
268+
* locks sooner.
234269
*/
270+
if (vacstmt->vacuum)
271+
{
272+
use_own_xacts= true;
273+
}
274+
else
275+
{
276+
Assert(vacstmt->analyze);
277+
if (in_outer_xact)
278+
use_own_xacts= false;
279+
elseif (length(relations)>1)
280+
use_own_xacts= true;
281+
else
282+
use_own_xacts= false;
283+
}
284+
285+
/*
286+
* If we are running ANALYZE without per-table transactions, we'll
287+
* need a memory context with table lifetime.
288+
*/
289+
if (!use_own_xacts)
290+
anl_context=AllocSetContextCreate(PortalContext,
291+
"Analyze",
292+
ALLOCSET_DEFAULT_MINSIZE,
293+
ALLOCSET_DEFAULT_INITSIZE,
294+
ALLOCSET_DEFAULT_MAXSIZE);
235295

236296
/*
237-
* The strangeness with committing and starting transactions here is
238-
* due to wanting to run each table's VACUUM as a separate
239-
* transaction, so that we don't hold locks unnecessarily long. Also,
240-
* if we are doing VACUUM ANALYZE, the ANALYZE part runs as a separate
241-
* transaction from the VACUUM to further reduce locking.
242-
*
243297
* vacuum_rel expects to be entered with no transaction active; it will
244298
* start and commit its own transaction. But we are called by an SQL
245299
* command, and so we are executing inside a transaction already. We
246300
* commit the transaction started in PostgresMain() here, and start
247301
* another one before exiting to match the commit waiting for us back
248302
* in PostgresMain().
249-
*
250-
* In the case of an ANALYZE statement (no vacuum, just analyze) it's
251-
* okay to run the whole thing in the outer transaction, and so we
252-
* skip transaction start/stop operations.
253303
*/
254-
if (vacstmt->vacuum)
304+
if (use_own_xacts)
255305
{
256-
if (all_rels)
257-
{
258-
/*
259-
* It's a database-wide VACUUM.
260-
*
261-
* Compute the initially applicable OldestXmin and FreezeLimit
262-
* XIDs, so that we can record these values at the end of the
263-
* VACUUM. Note that individual tables may well be processed
264-
* with newer values, but we can guarantee that no
265-
* (non-shared) relations are processed with older ones.
266-
*
267-
* It is okay to record non-shared values in pg_database, even
268-
* though we may vacuum shared relations with older cutoffs,
269-
* because only the minimum of the values present in
270-
* pg_database matters. We can be sure that shared relations
271-
* have at some time been vacuumed with cutoffs no worse than
272-
* the global minimum; for, if there is a backend in some
273-
* other DB with xmin = OLDXMIN that's determining the cutoff
274-
* with which we vacuum shared relations, it is not possible
275-
* for that database to have a cutoff newer than OLDXMIN
276-
* recorded in pg_database.
277-
*/
278-
vacuum_set_xid_limits(vacstmt, false,
279-
&initialOldestXmin,
280-
&initialFreezeLimit);
281-
}
282-
283306
/* matches the StartTransaction in PostgresMain() */
284307
CommitTransactionCommand();
285308
}
@@ -301,13 +324,13 @@ vacuum(VacuumStmt *vacstmt)
301324
MemoryContextold_context=NULL;
302325

303326
/*
304-
* Ifwe vacuumed, use new transaction for analyze. Otherwise,
327+
* Ifusing separate xacts, start one for analyze. Otherwise,
305328
* we can use the outer transaction, but we still need to call
306329
* analyze_rel in a memory context that will be cleaned up on
307330
* return (else we leak memory while processing multiple
308331
* tables).
309332
*/
310-
if (vacstmt->vacuum)
333+
if (use_own_xacts)
311334
{
312335
StartTransactionCommand();
313336
SetQuerySnapshot();/* might be needed for functions
@@ -326,7 +349,7 @@ vacuum(VacuumStmt *vacstmt)
326349

327350
StrategyHintVacuum(false);
328351

329-
if (vacstmt->vacuum)
352+
if (use_own_xacts)
330353
CommitTransactionCommand();
331354
else
332355
{
@@ -339,7 +362,7 @@ vacuum(VacuumStmt *vacstmt)
339362
/*
340363
* Finish up processing.
341364
*/
342-
if (vacstmt->vacuum)
365+
if (use_own_xacts)
343366
{
344367
/* here, we are not in a transaction */
345368

@@ -348,7 +371,10 @@ vacuum(VacuumStmt *vacstmt)
348371
* PostgresMain().
349372
*/
350373
StartTransactionCommand();
374+
}
351375

376+
if (vacstmt->vacuum)
377+
{
352378
/*
353379
* If it was a database-wide VACUUM, print FSM usage statistics
354380
* (we don't make you be superuser to see these).

‎src/include/access/xact.h

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/access/xact.h,v 1.62 2004/04/05 03:11:39 momjian Exp $
10+
* $PostgreSQL: pgsql/src/include/access/xact.h,v 1.63 2004/05/22 23:14:38 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -145,6 +145,7 @@ extern void UserAbortTransactionBlock(void);
145145
externvoidAbortOutOfAnyTransaction(void);
146146
externvoidPreventTransactionChain(void*stmtNode,constchar*stmtType);
147147
externvoidRequireTransactionChain(void*stmtNode,constchar*stmtType);
148+
externboolIsInTransactionChain(void*stmtNode);
148149
externvoidRegisterEOXactCallback(EOXactCallbackcallback,void*arg);
149150
externvoidUnregisterEOXactCallback(EOXactCallbackcallback,void*arg);
150151

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