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Predicate locking in hash indexes.

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Hash index searches acquire predicate locks on the primary
page of a bucket. It acquires a lock on both the old and new buckets
for scans that happen concurrently with page splits. During a bucket
split, a predicate lock is copied from the primary page of an old
bucket to the primary page of a new bucket.

Author: Shubham Barai, Amit Kapila
Reviewed by: Amit Kapila, Alexander Korotkov, Thomas Munro
Discussion: https://www.postgresql.org/message-id/flat/CALxAEPvNsM2GTiXdRgaaZ1Pjd1bs+sxfFsf7Ytr+iq+5JJoYXA@mail.gmail.com
This commit is contained in:
Teodor Sigaev
2018-04-07 16:59:14 +03:00
parent 971d7ddbe1
commit b508a56f2f
8 changed files with 802 additions and 1 deletions
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2
src/backend/access/hash/hash.c
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@ -68,7 +68,7 @@ hashhandler(PG_FUNCTION_ARGS)
amroutine->amsearchnulls = false;
amroutine->amstorage = false;
amroutine->amclusterable = false;
amroutine->ampredlocks = false;
amroutine->ampredlocks = true;
amroutine->amcanparallel = false;
amroutine->amkeytype = INT4OID;

3
src/backend/access/hash/hashinsert.c
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@ -22,6 +22,7 @@
#include "utils/rel.h"
#include "storage/lwlock.h"
#include "storage/buf_internals.h"
#include "storage/predicate.h"
static void _hash_vacuum_one_page(Relation rel, Buffer metabuf, Buffer buf,
RelFileNode hnode);
@ -88,6 +89,8 @@ restart_insert:
&usedmetap);
Assert(usedmetap != NULL);
CheckForSerializableConflictIn(rel, NULL, buf);
/* remember the primary bucket buffer to release the pin on it at end. */
bucket_buf = buf;

6
src/backend/access/hash/hashpage.c
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@ -33,6 +33,7 @@
#include "miscadmin.h"
#include "storage/lmgr.h"
#include "storage/smgr.h"
#include "storage/predicate.h"
static bool _hash_alloc_buckets(Relation rel, BlockNumber firstblock,
@ -1107,6 +1108,11 @@ _hash_splitbucket(Relation rel,
npage = BufferGetPage(nbuf);
nopaque = (HashPageOpaque) PageGetSpecialPointer(npage);
/* Copy the predicate locks from old bucket to new bucket. */
PredicateLockPageSplit(rel,
BufferGetBlockNumber(bucket_obuf),
BufferGetBlockNumber(bucket_nbuf));
/*
* Partition the tuples in the old bucket between the old bucket and the
* new bucket, advancing along the old bucket's overflow bucket chain and

3
src/backend/access/hash/hashsearch.c
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@ -19,6 +19,7 @@
#include "miscadmin.h"
#include "pgstat.h"
#include "utils/rel.h"
#include "storage/predicate.h"
static bool _hash_readpage(IndexScanDesc scan, Buffer *bufP,
ScanDirection dir);
@ -171,6 +172,7 @@ _hash_readnext(IndexScanDesc scan,
Assert(BufferIsValid(*bufp));
LockBuffer(*bufp, BUFFER_LOCK_SHARE);
PredicateLockPage(rel, BufferGetBlockNumber(*bufp), scan->xs_snapshot);
/*
* setting hashso_buc_split to true indicates that we are scanning
@ -347,6 +349,7 @@ _hash_first(IndexScanDesc scan, ScanDirection dir)
so->hashso_sk_hash = hashkey;
buf = _hash_getbucketbuf_from_hashkey(rel, hashkey, HASH_READ, NULL);
PredicateLockPage(rel, BufferGetBlockNumber(buf), scan->xs_snapshot);
page = BufferGetPage(buf);
TestForOldSnapshot(scan->xs_snapshot, rel, page);
opaque = (HashPageOpaque) PageGetSpecialPointer(page);