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Port single-page btree vacuum logic to hash indexes.

Browse Source 
This is advantageous for hash indexes for the same reasons it's good
for btrees: it accelerates space recycling, reducing bloat.

Ashutosh Sharma, reviewed by Amit Kapila and by me.  A bit of
additional hacking by me.

Discussion: http://postgr.es/m/CAE9k0PkRSyzx8dOnokEpUi2A-RFZK72WN0h9DEMv_ut9q6bPRw@mail.gmail.com
This commit is contained in:
Robert Haas
2017-03-15 22:18:56 -04:00
parent 2038bf41c9
commit 6977b8b7f4
10 changed files with 517 additions and 17 deletions
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68
src/backend/access/hash/hashutil.c
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@@ -19,6 +19,7 @@
#include "access/relscan.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "storage/buf_internals.h"
#define CALC_NEW_BUCKET(old_bucket, lowmask) \
old_bucket | (lowmask + 1)
@@ -446,3 +447,70 @@ _hash_get_newbucket_from_oldbucket(Relation rel, Bucket old_bucket,
return new_bucket;
}
/*
* _hash_kill_items - set LP_DEAD state for items an indexscan caller has
* told us were killed.
*
* scan->opaque, referenced locally through so, contains information about the
* current page and killed tuples thereon (generally, this should only be
* called if so->numKilled > 0).
*
* We match items by heap TID before assuming they are the right ones to
* delete.
*/
void
_hash_kill_items(IndexScanDesc scan)
{
HashScanOpaque so = (HashScanOpaque) scan->opaque;
Page page;
HashPageOpaque opaque;
OffsetNumber offnum, maxoff;
int numKilled = so->numKilled;
int i;
bool killedsomething = false;
Assert(so->numKilled > 0);
Assert(so->killedItems != NULL);
/*
* Always reset the scan state, so we don't look for same
* items on other pages.
*/
so->numKilled = 0;
page = BufferGetPage(so->hashso_curbuf);
opaque = (HashPageOpaque) PageGetSpecialPointer(page);
maxoff = PageGetMaxOffsetNumber(page);
for (i = 0; i < numKilled; i++)
{
offnum = so->killedItems[i].indexOffset;
while (offnum <= maxoff)
{
ItemId iid = PageGetItemId(page, offnum);
IndexTuple ituple = (IndexTuple) PageGetItem(page, iid);
if (ItemPointerEquals(&ituple->t_tid, &so->killedItems[i].heapTid))
{
/* found the item */
ItemIdMarkDead(iid);
killedsomething = true;
break; /* out of inner search loop */
}
offnum = OffsetNumberNext(offnum);
}
}
/*
* Since this can be redone later if needed, mark as dirty hint.
* Whenever we mark anything LP_DEAD, we also set the page's
* LH_PAGE_HAS_DEAD_TUPLES flag, which is likewise just a hint.
*/
if (killedsomething)
{
opaque->hasho_flag |= LH_PAGE_HAS_DEAD_TUPLES;
MarkBufferDirtyHint(so->hashso_curbuf, true);
}
}