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Change currtid functions to use an MVCC snapshot, not SnapshotNow.

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This has a slight performance cost, but the only known consumers
of these functions, known at the SQL level as currtid and currtid2,
is pgsql-odbc; whose usage, we hope, is not sufficiently intensive
to make this a problem.

Per discussion.
This commit is contained in:
Robert Haas 2013-07-25 16:32:02 -04:00
parent 80c79ab2a8
commit ed93feb808
1 changed files with 10 additions and 2 deletions
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12
src/backend/utils/adt/tid.c
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@ -30,6 +30,7 @@
#include "utils/acl.h" #include "utils/acl.h"
#include "utils/builtins.h" #include "utils/builtins.h"
#include "utils/rel.h" #include "utils/rel.h"
#include "utils/snapmgr.h"
#include "utils/tqual.h" #include "utils/tqual.h"
@ -332,6 +333,7 @@ currtid_byreloid(PG_FUNCTION_ARGS)
ItemPointer result; ItemPointer result;
Relation rel; Relation rel;
AclResult aclresult; AclResult aclresult;
Snapshot snapshot;
result = (ItemPointer) palloc(sizeof(ItemPointerData)); result = (ItemPointer) palloc(sizeof(ItemPointerData));
if (!reloid) if (!reloid)
@ -352,7 +354,10 @@ currtid_byreloid(PG_FUNCTION_ARGS)
return currtid_for_view(rel, tid); return currtid_for_view(rel, tid);
ItemPointerCopy(tid, result); ItemPointerCopy(tid, result);
heap_get_latest_tid(rel, SnapshotNow, result);
snapshot = RegisterSnapshot(GetLatestSnapshot());
heap_get_latest_tid(rel, snapshot, result);
UnregisterSnapshot(snapshot);
heap_close(rel, AccessShareLock); heap_close(rel, AccessShareLock);
@ -368,6 +373,7 @@ currtid_byrelname(PG_FUNCTION_ARGS)
RangeVar *relrv; RangeVar *relrv;
Relation rel; Relation rel;
AclResult aclresult; AclResult aclresult;
Snapshot snapshot;
relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname)); relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
rel = heap_openrv(relrv, AccessShareLock); rel = heap_openrv(relrv, AccessShareLock);
@ -384,7 +390,9 @@ currtid_byrelname(PG_FUNCTION_ARGS)
result = (ItemPointer) palloc(sizeof(ItemPointerData)); result = (ItemPointer) palloc(sizeof(ItemPointerData));
ItemPointerCopy(tid, result); ItemPointerCopy(tid, result);
heap_get_latest_tid(rel, SnapshotNow, result); snapshot = RegisterSnapshot(GetLatestSnapshot());
heap_get_latest_tid(rel, snapshot, result);
UnregisterSnapshot(snapshot);
heap_close(rel, AccessShareLock); heap_close(rel, AccessShareLock);