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Move the tuple freezing point in CLUSTER to a point further back in the past,

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to avoid losing useful Xid information in not-so-old tuples.  This makes
CLUSTER behave the same as VACUUM as far a tuple-freezing behavior goes
(though CLUSTER does not yet advance the table's relfrozenxid).

While at it, move the actual freezing operation in rewriteheap.c to a more
appropriate place, and document it thoroughly.  This part of the patch from
Tom Lane.
This commit is contained in:
Alvaro Herrera
2007-05-17 15:28:29 +00:00
parent 90cbc63fd1
commit 3b0347b36e
6 changed files with 44 additions and 21 deletions
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15
src/backend/commands/cluster.c
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@ -11,7 +11,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.159 2007/04/08 01:26:28 tgl Exp $
* $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.160 2007/05/17 15:28:29 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@ -29,6 +29,7 @@
#include "catalog/namespace.h"
#include "catalog/toasting.h"
#include "commands/cluster.h"
#include "commands/vacuum.h"
#include "miscadmin.h"
#include "storage/procarray.h"
#include "utils/acl.h"
@ -657,6 +658,7 @@ copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex)
HeapTuple tuple;
bool use_wal;
TransactionId OldestXmin;
TransactionId FreezeXid;
RewriteState rwstate;
/*
@ -688,11 +690,16 @@ copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex)
/* use_wal off requires rd_targblock be initially invalid */
Assert(NewHeap->rd_targblock == InvalidBlockNumber);
/* Get the cutoff xmin we'll use to weed out dead tuples */
OldestXmin = GetOldestXmin(OldHeap->rd_rel->relisshared, true);
/*
* compute xids used to freeze and weed out dead tuples. We use -1
* freeze_min_age to avoid having CLUSTER freeze tuples earlier than
* a plain VACUUM would.
*/
vacuum_set_xid_limits(-1, OldHeap->rd_rel->relisshared,
&OldestXmin, &FreezeXid);
/* Initialize the rewrite operation */
rwstate = begin_heap_rewrite(NewHeap, OldestXmin, use_wal);
rwstate = begin_heap_rewrite(NewHeap, OldestXmin, FreezeXid, use_wal);
/*
* Scan through the OldHeap in OldIndex order and copy each tuple into the