For multi-table ANALYZE, use per-table transactions when possible
(ie, when not inside a transaction block), so that we can avoid holding locks longer than necessary. Per trouble report from Philip Warner.
This commit is contained in:
Tom Lane
parent
e26c403fd0
commit
4d86ae4260
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.166 2004/05/21 05:07:56 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.167 2004/05/22 23:14:37 tgl Exp $
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*
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* NOTES
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* Transaction aborts can now occur two ways:
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@ -1417,7 +1417,7 @@ PreventTransactionChain(void *stmtNode, const char *stmtType)
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errmsg("%s cannot be executed from a function", stmtType)));
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/* If we got past IsTransactionBlock test, should be in default state */
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if (CurrentTransactionState->blockState != TBLOCK_DEFAULT &&
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CurrentTransactionState->blockState != TBLOCK_STARTED)
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CurrentTransactionState->blockState != TBLOCK_STARTED)
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elog(ERROR, "cannot prevent transaction chain");
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/* all okay */
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}
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@ -1462,6 +1462,36 @@ RequireTransactionChain(void *stmtNode, const char *stmtType)
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stmtType)));
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}
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/*
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* IsInTransactionChain
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*
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* This routine is for statements that need to behave differently inside
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* a transaction block than when running as single commands. ANALYZE is
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* currently the only example.
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*
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* stmtNode: pointer to parameter block for statement; this is used in
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* a very klugy way to determine whether we are inside a function.
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*/
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bool
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IsInTransactionChain(void *stmtNode)
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{
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/*
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* Return true on same conditions that would make PreventTransactionChain
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* error out
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*/
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if (IsTransactionBlock())
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return true;
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if (!MemoryContextContains(QueryContext, stmtNode))
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return true;
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if (CurrentTransactionState->blockState != TBLOCK_DEFAULT &&
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CurrentTransactionState->blockState != TBLOCK_STARTED)
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return true;
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return false;
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}
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/*
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* Register or deregister callback functions for end-of-xact cleanup
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@ -13,7 +13,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.276 2004/05/21 16:08:46 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.277 2004/05/22 23:14:38 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -161,7 +161,9 @@ vacuum(VacuumStmt *vacstmt)
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MemoryContext anl_context = NULL;
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TransactionId initialOldestXmin = InvalidTransactionId;
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TransactionId initialFreezeLimit = InvalidTransactionId;
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bool all_rels;
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bool all_rels,
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in_outer_xact,
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use_own_xacts;
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List *relations,
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*cur;
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@ -177,10 +179,23 @@ vacuum(VacuumStmt *vacstmt)
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* Furthermore, the forced commit that occurs before truncating the
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* relation's file would have the effect of committing the rest of the
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* user's transaction too, which would certainly not be the desired
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* behavior.
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* behavior. (This only applies to VACUUM FULL, though. We could
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* in theory run lazy VACUUM inside a transaction block, but we choose
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* to disallow that case because we'd rather commit as soon as possible
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* after finishing the vacuum. This is mainly so that we can let go the
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* AccessExclusiveLock that we may be holding.)
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*
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* ANALYZE (without VACUUM) can run either way.
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*/
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if (vacstmt->vacuum)
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{
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PreventTransactionChain((void *) vacstmt, stmttype);
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in_outer_xact = false;
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}
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else
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{
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in_outer_xact = IsInTransactionChain((void *) vacstmt);
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}
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/* Turn vacuum cost accounting on or off */
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VacuumCostActive = (VacuumCostNaptime > 0);
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@ -205,81 +220,89 @@ vacuum(VacuumStmt *vacstmt)
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ALLOCSET_DEFAULT_INITSIZE,
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ALLOCSET_DEFAULT_MAXSIZE);
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/*
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* If we are running only ANALYZE, we don't need per-table
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* transactions, but we still need a memory context with table
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* lifetime.
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*/
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if (vacstmt->analyze && !vacstmt->vacuum)
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anl_context = AllocSetContextCreate(PortalContext,
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"Analyze",
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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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/* Assume we are processing everything unless one table is mentioned */
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all_rels = (vacstmt->relation == NULL);
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/* Build list of relations to process (note this lives in vac_context) */
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relations = get_rel_oids(vacstmt->relation, stmttype);
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/*
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* Formerly, there was code here to prevent more than one VACUUM from
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* executing concurrently in the same database. However, there's no
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* good reason to prevent that, and manually removing lockfiles after
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* a vacuum crash was a pain for dbadmins. So, forget about
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* lockfiles, and just rely on the locks we grab on each target table
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* to ensure that there aren't two VACUUMs running on the same table
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* at the same time.
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*/
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if (vacstmt->vacuum && all_rels)
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{
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/*
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* It's a database-wide VACUUM.
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*
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* Compute the initially applicable OldestXmin and FreezeLimit
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* XIDs, so that we can record these values at the end of the
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* VACUUM. Note that individual tables may well be processed
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* with newer values, but we can guarantee that no
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* (non-shared) relations are processed with older ones.
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*
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* It is okay to record non-shared values in pg_database, even
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* though we may vacuum shared relations with older cutoffs,
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* because only the minimum of the values present in
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* pg_database matters. We can be sure that shared relations
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* have at some time been vacuumed with cutoffs no worse than
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* the global minimum; for, if there is a backend in some
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* other DB with xmin = OLDXMIN that's determining the cutoff
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* with which we vacuum shared relations, it is not possible
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* for that database to have a cutoff newer than OLDXMIN
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* recorded in pg_database.
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*/
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vacuum_set_xid_limits(vacstmt, false,
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&initialOldestXmin,
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&initialFreezeLimit);
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}
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/*
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* The strangeness with committing and starting transactions here is
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* due to wanting to run each table's VACUUM as a separate
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* transaction, so that we don't hold locks unnecessarily long. Also,
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* if we are doing VACUUM ANALYZE, the ANALYZE part runs as a separate
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* transaction from the VACUUM to further reduce locking.
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* Decide whether we need to start/commit our own transactions.
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*
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* For VACUUM (with or without ANALYZE): always do so, so that we
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* can release locks as soon as possible. (We could possibly use the
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* outer transaction for a one-table VACUUM, but handling TOAST tables
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* would be problematic.)
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*
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* For ANALYZE (no VACUUM): if inside a transaction block, we cannot
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* start/commit our own transactions. Also, there's no need to do so
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* if only processing one relation. For multiple relations when not
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* within a transaction block, use own transactions so we can release
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* locks sooner.
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*/
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if (vacstmt->vacuum)
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{
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use_own_xacts = true;
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}
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else
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{
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Assert(vacstmt->analyze);
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if (in_outer_xact)
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use_own_xacts = false;
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else if (length(relations) > 1)
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use_own_xacts = true;
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else
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use_own_xacts = false;
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}
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/*
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* If we are running ANALYZE without per-table transactions, we'll
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* need a memory context with table lifetime.
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*/
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if (!use_own_xacts)
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anl_context = AllocSetContextCreate(PortalContext,
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"Analyze",
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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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/*
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* vacuum_rel expects to be entered with no transaction active; it will
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* start and commit its own transaction. But we are called by an SQL
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* command, and so we are executing inside a transaction already. We
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* commit the transaction started in PostgresMain() here, and start
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* another one before exiting to match the commit waiting for us back
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* in PostgresMain().
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*
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* In the case of an ANALYZE statement (no vacuum, just analyze) it's
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* okay to run the whole thing in the outer transaction, and so we
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* skip transaction start/stop operations.
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*/
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if (vacstmt->vacuum)
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if (use_own_xacts)
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{
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if (all_rels)
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{
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/*
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* It's a database-wide VACUUM.
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*
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* Compute the initially applicable OldestXmin and FreezeLimit
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* XIDs, so that we can record these values at the end of the
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* VACUUM. Note that individual tables may well be processed
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* with newer values, but we can guarantee that no
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* (non-shared) relations are processed with older ones.
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*
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* It is okay to record non-shared values in pg_database, even
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* though we may vacuum shared relations with older cutoffs,
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* because only the minimum of the values present in
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* pg_database matters. We can be sure that shared relations
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* have at some time been vacuumed with cutoffs no worse than
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* the global minimum; for, if there is a backend in some
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* other DB with xmin = OLDXMIN that's determining the cutoff
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* with which we vacuum shared relations, it is not possible
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* for that database to have a cutoff newer than OLDXMIN
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* recorded in pg_database.
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*/
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vacuum_set_xid_limits(vacstmt, false,
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&initialOldestXmin,
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&initialFreezeLimit);
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}
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/* matches the StartTransaction in PostgresMain() */
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CommitTransactionCommand();
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}
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@ -301,13 +324,13 @@ vacuum(VacuumStmt *vacstmt)
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MemoryContext old_context = NULL;
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/*
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* If we vacuumed, use new transaction for analyze. Otherwise,
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* If using separate xacts, start one for analyze. Otherwise,
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* we can use the outer transaction, but we still need to call
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* analyze_rel in a memory context that will be cleaned up on
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* return (else we leak memory while processing multiple
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* tables).
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*/
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if (vacstmt->vacuum)
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if (use_own_xacts)
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{
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StartTransactionCommand();
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SetQuerySnapshot(); /* might be needed for functions
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@ -326,7 +349,7 @@ vacuum(VacuumStmt *vacstmt)
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StrategyHintVacuum(false);
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if (vacstmt->vacuum)
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if (use_own_xacts)
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CommitTransactionCommand();
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else
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{
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@ -339,7 +362,7 @@ vacuum(VacuumStmt *vacstmt)
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/*
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* Finish up processing.
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*/
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if (vacstmt->vacuum)
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if (use_own_xacts)
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{
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/* here, we are not in a transaction */
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@ -348,7 +371,10 @@ vacuum(VacuumStmt *vacstmt)
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* PostgresMain().
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*/
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StartTransactionCommand();
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}
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if (vacstmt->vacuum)
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{
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/*
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* If it was a database-wide VACUUM, print FSM usage statistics
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* (we don't make you be superuser to see these).
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/access/xact.h,v 1.62 2004/04/05 03:11:39 momjian Exp $
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* $PostgreSQL: pgsql/src/include/access/xact.h,v 1.63 2004/05/22 23:14:38 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -145,6 +145,7 @@ extern void UserAbortTransactionBlock(void);
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extern void AbortOutOfAnyTransaction(void);
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extern void PreventTransactionChain(void *stmtNode, const char *stmtType);
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extern void RequireTransactionChain(void *stmtNode, const char *stmtType);
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extern bool IsInTransactionChain(void *stmtNode);
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extern void RegisterEOXactCallback(EOXactCallback callback, void *arg);
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extern void UnregisterEOXactCallback(EOXactCallback callback, void *arg);
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