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The 1st step to implement new type of scan,TidScan.

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Now WHERE restriction on ctid is allowed though it is
sequentially scanned.
This commit is contained in:
Hiroshi Inoue
1999-10-11 06:28:29 +00:00
parent 65a2c8f5b8
commit 05d13cad28
6 changed files with 238 additions and 10 deletions
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91
src/backend/access/heap/heapam.c
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@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/heap/heapam.c,v 1.55 1999/09/24 00:23:54 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/access/heap/heapam.c,v 1.56 1999/10/11 06:28:27 inoue Exp $
*
*
* INTERFACE ROUTINES
@ -1086,6 +1086,95 @@ heap_fetch(Relation relation,
}
}
/* ----------------
* heap_get_latest_tid - get the latest tid of a specified tuple
*
* ----------------
*/
ItemPointer
heap_get_latest_tid(Relation relation,
Snapshot snapshot,
ItemPointer tid)
{
ItemId lp;
Buffer buffer;
PageHeader dp;
OffsetNumber offnum;
HeapTupleData tp;
HeapTupleHeader t_data;
ItemPointerData ctid;
bool invalidBlock,linkend;
/* ----------------
* get the buffer from the relation descriptor
* Note that this does a buffer pin.
* ----------------
*/
buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid));
if (!BufferIsValid(buffer))
elog(ERROR, "heap_get_latest_tid: %s relation: ReadBuffer(%lx) failed",
&relation->rd_rel->relname, (long) tid);
LockBuffer(buffer, BUFFER_LOCK_SHARE);
/* ----------------
* get the item line pointer corresponding to the requested tid
* ----------------
*/
dp = (PageHeader) BufferGetPage(buffer);
offnum = ItemPointerGetOffsetNumber(tid);
invalidBlock = true;
if (!PageIsNew(dp))
{
lp = PageGetItemId(dp, offnum);
if (ItemIdIsUsed(lp))
invalidBlock = false;
}
if (invalidBlock)
{
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
ReleaseBuffer(buffer);
return NULL;
}
/* ----------------
* more sanity checks
* ----------------
*/
t_data = tp.t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
tp.t_len = ItemIdGetLength(lp);
tp.t_self = *tid;
ctid = tp.t_data->t_ctid;
/* ----------------
* check time qualification of tid
* ----------------
*/
HeapTupleSatisfies(&tp, relation, buffer, dp,
snapshot, 0, (ScanKey) NULL);
linkend = true;
if ((t_data->t_infomask & HEAP_XMAX_COMMITTED) &&
!ItemPointerEquals(tid, &ctid))
linkend = false;
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
ReleaseBuffer(buffer);
if (tp.t_data == NULL)
{
if (linkend)
return NULL;
return heap_get_latest_tid(relation, snapshot, &ctid);
}
return tid;
}
/* ----------------
* heap_insert - insert tuple
*