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Simplified locking for entry point

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This commit is contained in:
Andrew Kane
2023-08-21 03:22:23 -07:00
parent 02f4e0ec8b
commit d4fe67e8ee
1 changed files with 15 additions and 54 deletions
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69
src/hnswinsert.c
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@@ -402,50 +402,6 @@ HnswUpdateNeighborPages(Relation index, FmgrInfo *procinfo, Oid collation, HnswE
}
}
/*
* Add the entry point
*/
static bool
HnswAddEntryPoint(Relation index, HnswElement element, int m, HnswElement * entryPoint)
{
Buffer buf;
Page page;
GenericXLogState *state;
HnswMetaPage metap;
BlockNumber newInsertPage = InvalidBlockNumber;
/* Lock the metapage to prevent concurrent inserts */
buf = ReadBuffer(index, HNSW_METAPAGE_BLKNO);
LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
page = BufferGetPage(buf);
metap = HnswPageGetMeta(page);
/* Check for new entry point after lock is acquired */
if (BlockNumberIsValid(metap->entryBlkno))
{
*entryPoint = HnswInitElementFromBlock(metap->entryBlkno, metap->entryOffno);
UnlockReleaseBuffer(buf);
return false;
}
/* Write element and neighbor tuples */
WriteNewElementPages(index, element, m, metap->insertPage, &newInsertPage);
/* Start WAL */
state = GenericXLogStart(index);
page = GenericXLogRegisterBuffer(state, buf, 0);
/* Update the metapage info */
HnswUpdateMetaPageInfo(page, HNSW_UPDATE_ENTRY_ALWAYS, element, newInsertPage);
/* Commit and unlock */
HnswCommitBuffer(buf, state);
return true;
}
/*
* Add a heap TID to an existing element
*/
@@ -522,7 +478,7 @@ WriteElement(Relation index, FmgrInfo *procinfo, Oid collation, HnswElement elem
HnswUpdateNeighborPages(index, procinfo, collation, element, m, false);
/* Update metapage if needed */
if (element->level > entryPoint->level)
if (entryPoint == NULL || element->level > entryPoint->level)
HnswUpdateMetaPage(index, HNSW_UPDATE_ENTRY_GREATER, element, InvalidBlockNumber, MAIN_FORKNUM);
}
@@ -542,6 +498,7 @@ HnswInsertTuple(Relation index, Datum *values, bool *isnull, ItemPointer heap_ti
FmgrInfo *procinfo = index_getprocinfo(index, 1, HNSW_DISTANCE_PROC);
Oid collation = index->rd_indcollation[0];
HnswElement dup;
LOCKMODE lockmode = ShareLock;
/* Detoast once for all calls */
value = PointerGetDatum(PG_DETOAST_DATUM(values[0]));
@@ -562,19 +519,23 @@ HnswInsertTuple(Relation index, Datum *values, bool *isnull, ItemPointer heap_ti
* Get a shared lock for the duration of the insert. Use a page lock so it
* does not interfere with buffer lock (or reads when vacuuming).
*/
LockPage(index, HNSW_METAPAGE_BLKNO, ShareLock);
LockPage(index, HNSW_METAPAGE_BLKNO, lockmode);
/* Get entry point */
entryPoint = HnswGetEntryPoint(index);
/* Prevent concurrent inserts when no entry point */
if (entryPoint == NULL)
/* Prevent concurrent inserts when likely updating entry point */
if (entryPoint == NULL || element->level > entryPoint->level)
{
if (HnswAddEntryPoint(index, element, m, &entryPoint))
{
UnlockPage(index, HNSW_METAPAGE_BLKNO, ShareLock);
return true;
}
/* Release shared lock */
UnlockPage(index, HNSW_METAPAGE_BLKNO, lockmode);
/* Get exclusive lock */
lockmode = ExclusiveLock;
LockPage(index, HNSW_METAPAGE_BLKNO, lockmode);
/* Get latest entry point after lock is acquired */
entryPoint = HnswGetEntryPoint(index);
}
/* Insert element in graph */
@@ -587,7 +548,7 @@ HnswInsertTuple(Relation index, Datum *values, bool *isnull, ItemPointer heap_ti
WriteElement(index, procinfo, collation, element, m, efConstruction, dup, entryPoint);
/* Release shared lock */
UnlockPage(index, HNSW_METAPAGE_BLKNO, ShareLock);
UnlockPage(index, HNSW_METAPAGE_BLKNO, lockmode);
return true;
}