Better solution to integer overflow problem in hash batch-number

computation: reduce the bucket number mod nbatch.  This changes the
association between original bucket numbers and batches, but that
doesn't matter.  Minor other cleanups in hashjoin code to help
centralize decisions.

src/backend/executor/nodeHash.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeHash.c,v 1.72 2002/12/29 22:28:50 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeHash.c,v 1.73 2002/12/30 15:21:18 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -59,9 +59,6 @@ ExecHash(HashState *node)
 	outerNode = outerPlanState(node);
 
 	hashtable = node->hashtable;
-	if (hashtable == NULL)
-		elog(ERROR, "ExecHash: hash table is NULL.");
-
 	nbatch = hashtable->nbatch;
 
 	if (nbatch > 0)
@@ -284,20 +281,13 @@ ExecHashTableCreate(Hash *node)
 		 * allocate and initialize the file arrays in hashCxt
 		 */
 		hashtable->innerBatchFile = (BufFile **)
-			palloc(nbatch * sizeof(BufFile *));
+			palloc0(nbatch * sizeof(BufFile *));
 		hashtable->outerBatchFile = (BufFile **)
-			palloc(nbatch * sizeof(BufFile *));
+			palloc0(nbatch * sizeof(BufFile *));
 		hashtable->innerBatchSize = (long *)
-			palloc(nbatch * sizeof(long));
+			palloc0(nbatch * sizeof(long));
 		hashtable->outerBatchSize = (long *)
-			palloc(nbatch * sizeof(long));
-		for (i = 0; i < nbatch; i++)
-		{
-			hashtable->innerBatchFile[i] = NULL;
-			hashtable->outerBatchFile[i] = NULL;
-			hashtable->innerBatchSize[i] = 0;
-			hashtable->outerBatchSize[i] = 0;
-		}
+			palloc0(nbatch * sizeof(long));
 		/* The files will not be opened until later... */
 	}
 
@@ -308,13 +298,7 @@ ExecHashTableCreate(Hash *node)
 	MemoryContextSwitchTo(hashtable->batchCxt);
 
 	hashtable->buckets = (HashJoinTuple *)
-		palloc(nbuckets * sizeof(HashJoinTuple));
-
-	if (hashtable->buckets == NULL)
-		elog(ERROR, "Insufficient memory for hash table.");
-
-	for (i = 0; i < nbuckets; i++)
-		hashtable->buckets[i] = NULL;
+		palloc0(nbuckets * sizeof(HashJoinTuple));
 
 	MemoryContextSwitchTo(oldcxt);
 
@@ -414,15 +398,14 @@ ExecChooseHashTableSize(double ntuples, int tupwidth,
 		 * totalbuckets/nbuckets; in fact, it is the number of groups we
 		 * will use for the part of the data that doesn't fall into the
 		 * first nbuckets hash buckets.  We try to set it to make all the
-		 * batches the same size.  But we have to keep nbatch small
-		 * enough to avoid integer overflow in ExecHashJoinGetBatch().
+		 * batches the same size.
 		 */
 		dtmp = ceil((inner_rel_bytes - hash_table_bytes) /
 					hash_table_bytes);
-		if (dtmp < INT_MAX / totalbuckets)
+		if (dtmp < INT_MAX)
 			nbatch = (int) dtmp;
 		else
-			nbatch = INT_MAX / totalbuckets;
+			nbatch = INT_MAX;
 		if (nbatch <= 0)
 			nbatch = 1;
 	}
@@ -481,13 +464,14 @@ ExecHashTableInsert(HashJoinTable hashtable,
 					List *hashkeys)
 {
 	int			bucketno = ExecHashGetBucket(hashtable, econtext, hashkeys);
+	int			batchno = ExecHashGetBatch(bucketno, hashtable);
 	TupleTableSlot *slot = econtext->ecxt_innertuple;
 	HeapTuple	heapTuple = slot->val;
 
 	/*
 	 * decide whether to put the tuple in the hash table or a tmp file
 	 */
-	if (bucketno < hashtable->nbuckets)
+	if (batchno < 0)
 	{
 		/*
 		 * put the tuple in hash table
@@ -498,8 +482,6 @@ ExecHashTableInsert(HashJoinTable hashtable,
 		hashTupleSize = MAXALIGN(sizeof(*hashTuple)) + heapTuple->t_len;
 		hashTuple = (HashJoinTuple) MemoryContextAlloc(hashtable->batchCxt,
 													   hashTupleSize);
-		if (hashTuple == NULL)
-			elog(ERROR, "Insufficient memory for hash table.");
 		memcpy((char *) &hashTuple->htup,
 			   (char *) heapTuple,
 			   sizeof(hashTuple->htup));
@@ -515,11 +497,8 @@ ExecHashTableInsert(HashJoinTable hashtable,
 	else
 	{
 		/*
-		 * put the tuple into a tmp file for other batches
+		 * put the tuple into a tmp file for later batches
 		 */
-		int			batchno = (hashtable->nbatch * (bucketno - hashtable->nbuckets)) /
-		(hashtable->totalbuckets - hashtable->nbuckets);
-
 		hashtable->innerBatchSize[batchno]++;
 		ExecHashJoinSaveTuple(heapTuple,
 							  hashtable->innerBatchFile[batchno]);
@@ -592,6 +571,24 @@ ExecHashGetBucket(HashJoinTable hashtable,
 	return bucketno;
 }
 
+/* ----------------------------------------------------------------
+ *		ExecHashGetBatch
+ *
+ *		determine the batch number for a bucketno
+ *
+ * Returns -1 if bucket belongs to initial (or current) batch,
+ * else 0..nbatch-1 corresponding to external batch file number for bucket.
+ * ----------------------------------------------------------------
+ */
+int
+ExecHashGetBatch(int bucketno, HashJoinTable hashtable)
+{
+	if (bucketno < hashtable->nbuckets)
+		return -1;
+
+	return (bucketno - hashtable->nbuckets) % hashtable->nbatch;
+}
+
 /* ----------------------------------------------------------------
  *		ExecScanHashBucket
  *
@@ -727,7 +724,6 @@ ExecHashTableReset(HashJoinTable hashtable, long ntuples)
 {
 	MemoryContext oldcxt;
 	int			nbuckets = hashtable->nbuckets;
-	int			i;
 
 	/*
 	 * Release all the hash buckets and tuples acquired in the prior pass,
@@ -750,13 +746,7 @@ ExecHashTableReset(HashJoinTable hashtable, long ntuples)
 
 	/* Reallocate and reinitialize the hash bucket headers. */
 	hashtable->buckets = (HashJoinTuple *)
-		palloc(nbuckets * sizeof(HashJoinTuple));
-
-	if (hashtable->buckets == NULL)
-		elog(ERROR, "Insufficient memory for hash table.");
-
-	for (i = 0; i < nbuckets; i++)
-		hashtable->buckets[i] = NULL;
+		palloc0(nbuckets * sizeof(HashJoinTuple));
 
 	MemoryContextSwitchTo(oldcxt);
 }

src/backend/executor/nodeHashjoin.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeHashjoin.c,v 1.45 2002/12/15 16:17:46 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeHashjoin.c,v 1.46 2002/12/30 15:21:20 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -27,7 +27,6 @@ static TupleTableSlot *ExecHashJoinOuterGetTuple(PlanState *node,
 static TupleTableSlot *ExecHashJoinGetSavedTuple(HashJoinState *hjstate,
 						  BufFile *file,
 						  TupleTableSlot *tupleSlot);
-static int	ExecHashJoinGetBatch(int bucketno, HashJoinTable hashtable);
 static int	ExecHashJoinNewBatch(HashJoinState *hjstate);
 
 
@@ -179,17 +178,15 @@ ExecHashJoin(HashJoinState *node)
 			 */
 			if (hashtable->curbatch == 0)
 			{
-				int			batch = ExecHashJoinGetBatch(node->hj_CurBucketNo,
-														 hashtable);
+				int			batchno = ExecHashGetBatch(node->hj_CurBucketNo,
+													   hashtable);
 
-				if (batch > 0)
+				if (batchno >= 0)
 				{
 					/*
 					 * Need to postpone this outer tuple to a later batch.
 					 * Save it in the corresponding outer-batch file.
 					 */
-					int			batchno = batch - 1;
-
 					hashtable->outerBatchSize[batchno]++;
 					ExecHashJoinSaveTuple(outerTupleSlot->val,
 									 hashtable->outerBatchFile[batchno]);
@@ -640,28 +637,6 @@ ExecHashJoinNewBatch(HashJoinState *hjstate)
 	return newbatch;
 }
 
-/* ----------------------------------------------------------------
- *		ExecHashJoinGetBatch
- *
- *		determine the batch number for a bucketno
- *		+----------------+-------+-------+ ... +-------+
- *		0			  nbuckets						 totalbuckets
- * batch		 0			 1		 2	   ...
- * ----------------------------------------------------------------
- */
-static int
-ExecHashJoinGetBatch(int bucketno, HashJoinTable hashtable)
-{
-	int			b;
-
-	if (bucketno < hashtable->nbuckets || hashtable->nbatch == 0)
-		return 0;
-
-	b = (hashtable->nbatch * (bucketno - hashtable->nbuckets)) /
-		(hashtable->totalbuckets - hashtable->nbuckets);
-	return b + 1;
-}
-
 /* ----------------------------------------------------------------
  *		ExecHashJoinSaveTuple
  *