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Add some marginal tweaks to eliminate memory leakages associated with

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subtransactions.  Trivial subxacts (such as a plpgsql exception block
containing no database access) now demonstrably leak zero bytes.
This commit is contained in:
Tom Lane
2004-09-16 20:17:49 +00:00
parent 86fff990b2
commit 257cccbe5e
6 changed files with 118 additions and 16 deletions
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57
src/backend/access/transam/xact.c
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@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.189 2004/09/16 16:58:26 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.190 2004/09/16 20:17:16 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -861,9 +861,6 @@ AtCommit_Memory(void)
/*
* AtSubCommit_Memory
*
* We do not throw away the child's CurTransactionContext, since the data
* it contains will be needed at upper commit.
*/
static void
AtSubCommit_Memory(void)
@ -875,6 +872,18 @@ AtSubCommit_Memory(void)
/* Return to parent transaction level's memory context. */
CurTransactionContext = s->parent->curTransactionContext;
MemoryContextSwitchTo(CurTransactionContext);
/*
* Ordinarily we cannot throw away the child's CurTransactionContext,
* since the data it contains will be needed at upper commit. However,
* if there isn't actually anything in it, we can throw it away. This
* avoids a small memory leak in the common case of "trivial" subxacts.
*/
if (MemoryContextIsEmpty(s->curTransactionContext))
{
MemoryContextDelete(s->curTransactionContext);
s->curTransactionContext = NULL;
}
}
/*
@ -890,13 +899,27 @@ AtSubCommit_childXids(void)
Assert(s->parent != NULL);
old_cxt = MemoryContextSwitchTo(s->parent->curTransactionContext);
/*
* We keep the child-XID lists in TopTransactionContext; this avoids
* setting up child-transaction contexts for what might be just a few
* bytes of grandchild XIDs.
*/
old_cxt = MemoryContextSwitchTo(TopTransactionContext);
s->parent->childXids = lappend_xid(s->parent->childXids,
s->transactionId);
s->parent->childXids = list_concat(s->parent->childXids, s->childXids);
s->childXids = NIL; /* ensure list not doubly referenced */
if (s->childXids != NIL)
{
s->parent->childXids = list_concat(s->parent->childXids,
s->childXids);
/*
* list_concat doesn't free the list header for the second list;
* do so here to avoid memory leakage (kluge)
*/
pfree(s->childXids);
s->childXids = NIL;
}
MemoryContextSwitchTo(old_cxt);
}
@ -1092,6 +1115,23 @@ AtSubAbort_Memory(void)
MemoryContextSwitchTo(TopTransactionContext);
}
/*
* AtSubAbort_childXids
*/
static void
AtSubAbort_childXids(void)
{
TransactionState s = CurrentTransactionState;
/*
* We keep the child-XID lists in TopTransactionContext (see
* AtSubCommit_childXids). This means we'd better free the list
* explicitly at abort to avoid leakage.
*/
list_free(s->childXids);
s->childXids = NIL;
}
/*
* RecordSubTransactionAbort
*/
@ -3317,7 +3357,10 @@ AbortSubTransaction(void)
/* Advertise the fact that we aborted in pg_clog. */
if (TransactionIdIsValid(s->transactionId))
{
RecordSubTransactionAbort();
AtSubAbort_childXids();
}
/* Post-abort cleanup */
CallSubXactCallbacks(SUBXACT_EVENT_ABORT_SUB, s->subTransactionId,