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Commit2a6c032

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Repair CLUSTER failure after ALTER TABLE SET WITHOUT OIDS. Turns out
there are corner cases involving dropping toasted columns in which theprevious coding would fail, too: the new version of the table might nothave any TOAST table, but we'd still propagate possibly-wide values ofdropped columns forward.
1 parent4f82112 commit2a6c032

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1 file changed

+62
-11
lines changed

1 file changed

+62
-11
lines changed

‎src/backend/commands/cluster.c

Lines changed: 62 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@
1111
*
1212
*
1313
* IDENTIFICATION
14-
* $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.131 2004/12/31 21:59:41 pgsql Exp $
14+
* $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.132 2005/02/06 20:19:08 tgl Exp $
1515
*
1616
*-------------------------------------------------------------------------
1717
*/
@@ -605,32 +605,80 @@ copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex)
605605
RelationNewHeap,
606606
OldHeap,
607607
OldIndex;
608+
TupleDescoldTupDesc;
609+
TupleDescnewTupDesc;
610+
intnatts;
611+
Datum*values;
612+
char*nulls;
608613
IndexScanDescscan;
609614
HeapTupletuple;
610615

611616
/*
612-
* Open the relations I need. Scan through the OldHeap on the OldIndex
613-
* and insert each tuple into the NewHeap.
617+
* Open the relations we need.
614618
*/
615619
NewHeap=heap_open(OIDNewHeap,AccessExclusiveLock);
616620
OldHeap=heap_open(OIDOldHeap,AccessExclusiveLock);
617621
OldIndex=index_open(OIDOldIndex);
618622

623+
/*
624+
* Their tuple descriptors should be exactly alike, but here we only
625+
* need assume that they have the same number of columns.
626+
*/
627+
oldTupDesc=RelationGetDescr(OldHeap);
628+
newTupDesc=RelationGetDescr(NewHeap);
629+
Assert(newTupDesc->natts==oldTupDesc->natts);
630+
631+
/* Preallocate values/nulls arrays */
632+
natts=newTupDesc->natts;
633+
values= (Datum*)palloc0(natts*sizeof(Datum));
634+
nulls= (char*)palloc(natts*sizeof(char));
635+
memset(nulls,'n',natts*sizeof(char));
636+
637+
/*
638+
* Scan through the OldHeap on the OldIndex and copy each tuple into the
639+
* NewHeap.
640+
*/
619641
scan=index_beginscan(OldHeap,OldIndex,SnapshotNow,0, (ScanKey)NULL);
620642

621643
while ((tuple=index_getnext(scan,ForwardScanDirection))!=NULL)
622644
{
623645
/*
624-
* We must copy the tuple because heap_insert() will overwrite the
625-
* commit-status fields of the tuple it's handed, and the
626-
* retrieved tuple will actually be in a disk buffer! Thus, the
627-
* source relation would get trashed, which is bad news if we
628-
* abort later on.(This was a bug in releases thru 7.0)
646+
* We cannot simply pass the tuple to heap_insert(), for several
647+
* reasons:
648+
*
649+
* 1. heap_insert() will overwrite the commit-status fields of the
650+
* tuple it's handed. This would trash the source relation, which is
651+
* bad news if we abort later on. (This was a bug in releases thru
652+
* 7.0)
653+
*
654+
* 2. We'd like to squeeze out the values of any dropped columns,
655+
* both to save space and to ensure we have no corner-case failures.
656+
* (It's possible for example that the new table hasn't got a TOAST
657+
* table and so is unable to store any large values of dropped cols.)
629658
*
630-
* Note that the copied tuple will have the original OID, if any, so
631-
* this does preserve OIDs.
659+
* 3. The tuple might not even be legal for the new table; this is
660+
* currently only known to happen as an after-effect of ALTER TABLE
661+
* SET WITHOUT OIDS.
662+
*
663+
* So, we must reconstruct the tuple from component Datums.
632664
*/
633-
HeapTuplecopiedTuple=heap_copytuple(tuple);
665+
HeapTuplecopiedTuple;
666+
inti;
667+
668+
heap_deformtuple(tuple,oldTupDesc,values,nulls);
669+
670+
/* Be sure to null out any dropped columns */
671+
for (i=0;i<natts;i++)
672+
{
673+
if (newTupDesc->attrs[i]->attisdropped)
674+
nulls[i]='n';
675+
}
676+
677+
copiedTuple=heap_formtuple(newTupDesc,values,nulls);
678+
679+
/* Preserve OID, if any */
680+
if (NewHeap->rd_rel->relhasoids)
681+
HeapTupleSetOid(copiedTuple,HeapTupleGetOid(tuple));
634682

635683
simple_heap_insert(NewHeap,copiedTuple);
636684

@@ -641,6 +689,9 @@ copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex)
641689

642690
index_endscan(scan);
643691

692+
pfree(values);
693+
pfree(nulls);
694+
644695
index_close(OldIndex);
645696
heap_close(OldHeap,NoLock);
646697
heap_close(NewHeap,NoLock);

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