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First steps towards index scans with heap access decoupled from index

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access: define new index access method functions 'amgetmulti' that can
fetch multiple TIDs per call.  (The functions exist but are totally
untested as yet.)  Since I was modifying pg_am anyway, remove the
no-longer-needed 'rel' parameter from amcostestimate functions, and
also remove the vestigial amowner column that was creating useless
work for Alvaro's shared-object-dependencies project.
Initdb forced due to changes in pg_am.
This commit is contained in:
Tom Lane
2005-03-27 23:53:05 +00:00
parent 351519affc
commit bf3dbb5881
20 changed files with 535 additions and 174 deletions
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71
src/backend/access/hash/hash.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.77 2005/03/21 01:23:57 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.78 2005/03/27 23:52:57 tgl Exp $
*
* NOTES
* This file contains only the public interface routines.
@@ -264,6 +264,75 @@ hashgettuple(PG_FUNCTION_ARGS)
}
/*
* hashgetmulti() -- get multiple tuples at once
*
* This is a somewhat generic implementation: it avoids lock reacquisition
* overhead, but there's no smarts about picking especially good stopping
* points such as index page boundaries.
*/
Datum
hashgetmulti(PG_FUNCTION_ARGS)
{
IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
ItemPointer tids = (ItemPointer) PG_GETARG_POINTER(1);
int32 max_tids = PG_GETARG_INT32(2);
int32 *returned_tids = (int32 *) PG_GETARG_POINTER(3);
HashScanOpaque so = (HashScanOpaque) scan->opaque;
Relation rel = scan->indexRelation;
bool res = true;
int32 ntids = 0;
/*
* We hold pin but not lock on current buffer while outside the hash
* AM. Reacquire the read lock here.
*/
if (BufferIsValid(so->hashso_curbuf))
_hash_chgbufaccess(rel, so->hashso_curbuf, HASH_NOLOCK, HASH_READ);
while (ntids < max_tids)
{
/*
* Start scan, or advance to next tuple.
*/
if (ItemPointerIsValid(&(scan->currentItemData)))
res = _hash_next(scan, ForwardScanDirection);
else
res = _hash_first(scan, ForwardScanDirection);
/*
* Skip killed tuples if asked to.
*/
if (scan->ignore_killed_tuples)
{
while (res)
{
Page page;
OffsetNumber offnum;
offnum = ItemPointerGetOffsetNumber(&(scan->currentItemData));
page = BufferGetPage(so->hashso_curbuf);
if (!ItemIdDeleted(PageGetItemId(page, offnum)))
break;
res = _hash_next(scan, ForwardScanDirection);
}
}
if (!res)
break;
/* Save tuple ID, and continue scanning */
tids[ntids] = scan->xs_ctup.t_self;
ntids++;
}
/* Release read lock on current buffer, but keep it pinned */
if (BufferIsValid(so->hashso_curbuf))
_hash_chgbufaccess(rel, so->hashso_curbuf, HASH_READ, HASH_NOLOCK);
*returned_tids = ntids;
PG_RETURN_BOOL(res);
}
/*
* hashbeginscan() -- start a scan on a hash index
*/