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Fix up gcc warnings, improve comments.

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This commit is contained in:
Tom Lane 2002-06-15 21:52:31 +00:00
parent 2da3742cf5
commit c63bc32c2c
1 changed files with 50 additions and 30 deletions
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80
src/backend/commands/vacuum.c
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@ -13,7 +13,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.228 2002/06/15 19:54:23 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.229 2002/06/15 21:52:31 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -158,9 +158,8 @@ static bool enough_space(VacPage vacpage, Size len);
void
vacuum(VacuumStmt *vacstmt)
{
MemoryContext anl_context,
old_context;
const char *stmttype = vacstmt->vacuum ? "VACUUM" : "ANALYZE";
MemoryContext anl_context = NULL;
List *vrl,
*cur;
@ -188,7 +187,8 @@ vacuum(VacuumStmt *vacstmt)
/*
* Send info about dead objects to the statistics collector
*/
pgstat_vacuum_tabstat();
if (vacstmt->vacuum)
pgstat_vacuum_tabstat();
/*
* Create special memory context for cross-transaction storage.
@ -203,6 +203,10 @@ vacuum(VacuumStmt *vacstmt)
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
/*
* If we are running only ANALYZE, we don't need per-table transactions,
* but we still need a memory context with table lifetime.
*/
if (vacstmt->analyze && !vacstmt->vacuum)
anl_context = AllocSetContextCreate(QueryContext,
"Analyze",
@ -214,28 +218,40 @@ vacuum(VacuumStmt *vacstmt)
vrl = getrels(vacstmt->relation, stmttype);
/*
* Formerly, there was code here to prevent more than one VACUUM from
* executing concurrently in the same database. However, there's no
* good reason to prevent that, and manually removing lockfiles after
* a vacuum crash was a pain for dbadmins. So, forget about lockfiles,
* and just rely on the locks we grab on each target table
* to ensure that there aren't two VACUUMs running on the same table
* at the same time.
* Formerly, there was code here to prevent more than one VACUUM from
* executing concurrently in the same database. However, there's no
* good reason to prevent that, and manually removing lockfiles after
* a vacuum crash was a pain for dbadmins. So, forget about lockfiles,
* and just rely on the locks we grab on each target table
* to ensure that there aren't two VACUUMs running on the same table
* at the same time.
*/
/*
* The strangeness with committing and starting transactions here is due
* to wanting to run each table's VACUUM as a separate transaction, so
* that we don't hold locks unnecessarily long. Also, if we are doing
* VACUUM ANALYZE, the ANALYZE part runs as a separate transaction from
* the VACUUM to further reduce locking.
*
* The strangeness with committing and starting transactions in the
* init and shutdown routines is due to the fact that the vacuum cleaner
* is invoked via an SQL command, and so is already executing inside
* a transaction. We need to leave ourselves in a predictable state
* on entry and exit to the vacuum cleaner. We commit the transaction
* started in PostgresMain() inside vacuum_init(), and start one in
* vacuum_shutdown() to match the commit waiting for us back in
* PostgresMain().
* vacuum_rel expects to be entered with no transaction active; it will
* start and commit its own transaction. But we are called by an SQL
* command, and so we are executing inside a transaction already. We
* commit the transaction started in PostgresMain() here, and start
* another one before exiting to match the commit waiting for us back in
* PostgresMain().
*
* In the case of an ANALYZE statement (no vacuum, just analyze) it's
* okay to run the whole thing in the outer transaction, and so we skip
* transaction start/stop operations.
*/
if (vacstmt->vacuum)
{
if (vacstmt->relation == NULL)
{
/*
* It's a database-wide VACUUM.
*
* Compute the initially applicable OldestXmin and FreezeLimit
* XIDs, so that we can record these values at the end of the
* VACUUM. Note that individual tables may well be processed with
@ -261,11 +277,7 @@ vacuum(VacuumStmt *vacstmt)
}
/*
* Process each selected relation. We are careful to process each
* relation in a separate transaction in order to avoid holding too
* many locks at one time. Also, if we are doing VACUUM ANALYZE, the
* ANALYZE part runs as a separate transaction from the VACUUM to
* further reduce locking.
* Loop to process each selected relation.
*/
foreach(cur, vrl)
{
@ -275,7 +287,14 @@ vacuum(VacuumStmt *vacstmt)
vacuum_rel(relid, vacstmt, RELKIND_RELATION);
if (vacstmt->analyze)
{
/* If we vacuumed, use new transaction for analyze. */
MemoryContext old_context = NULL;
/*
* If we vacuumed, use new transaction for analyze. Otherwise,
* we can use the outer transaction, but we still need to call
* analyze_rel in a memory context that will be cleaned up on
* return (else we leak memory while processing multiple tables).
*/
if (vacstmt->vacuum)
StartTransactionCommand();
else
@ -287,16 +306,18 @@ vacuum(VacuumStmt *vacstmt)
CommitTransactionCommand();
else
{
MemoryContextResetAndDeleteChildren(anl_context);
MemoryContextSwitchTo(old_context);
MemoryContextResetAndDeleteChildren(anl_context);
}
}
}
/* clean up */
/*
* Finish up processing.
*/
if (vacstmt->vacuum)
{
/* on entry, we are not in a transaction */
/* here, we are not in a transaction */
/* matches the CommitTransaction in PostgresMain() */
StartTransactionCommand();
@ -322,9 +343,8 @@ vacuum(VacuumStmt *vacstmt)
MemoryContextDelete(vac_context);
vac_context = NULL;
if (vacstmt->analyze && !vacstmt->vacuum)
if (anl_context)
MemoryContextDelete(anl_context);
}
/*