pgvector.git / summary / log / commit / refs

commit    d4fe67e8eefd3087e3df27b3bfd3d8cc7c29ea17
Author:   Andrew Kane <andrew@ankane.org>
Date:     Mon Aug 21 10:22:23 2023 +0000

    Simplified locking for entry point


 src/hnswinsert.c | 69 ++++++++++++--------------------------------------------
 1 file changed, 15 insertions(+), 54 deletions(-)

diff --git a/src/hnswinsert.c b/src/hnswinsert.c
index f0c3d2ad..ab5b98a5 100644
--- a/src/hnswinsert.c
+++ b/src/hnswinsert.c
@@ -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;
 }


[parent: 02f4e0ec8b0a]