Revise hash join code so that we can increase the number of batches

on-the-fly, and thereby avoid blowing out memory when the planner has
underestimated the hash table size.  Hash join will now obey the
work_mem limit with some faithfulness.  Per my recent proposal
(hash aggregate part isn't done yet though).

src/backend/executor/nodeHash.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeHash.c,v 1.88 2004/12/31 21:59:45 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeHash.c,v 1.89 2005/03/06 22:15:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,6 +21,7 @@
 #include "postgres.h"
 
 #include "executor/execdebug.h"
+#include "executor/hashjoin.h"
 #include "executor/nodeHash.h"
 #include "executor/nodeHashjoin.h"
 #include "miscadmin.h"
@@ -29,6 +30,9 @@
 #include "utils/lsyscache.h"
 
 
+static void ExecHashIncreaseNumBatches(HashJoinTable hashtable);
+
+
 /* ----------------------------------------------------------------
  *		ExecHash
  *
@@ -39,33 +43,19 @@
 TupleTableSlot *
 ExecHash(HashState *node)
 {
-	EState	   *estate;
 	PlanState  *outerNode;
 	List	   *hashkeys;
 	HashJoinTable hashtable;
 	TupleTableSlot *slot;
 	ExprContext *econtext;
-	int			nbatch;
-	int			i;
+	uint32		hashvalue;
 
 	/*
 	 * get state info from node
 	 */
-	estate = node->ps.state;
 	outerNode = outerPlanState(node);
 
 	hashtable = node->hashtable;
-	nbatch = hashtable->nbatch;
-
-	if (nbatch > 0)
-	{
-		/*
-		 * Open temp files for inner batches, if needed. Note that file
-		 * buffers are palloc'd in regular executor context.
-		 */
-		for (i = 0; i < nbatch; i++)
-			hashtable->innerBatchFile[i] = BufFileCreateTemp(false);
-	}
 
 	/*
 	 * set expression context
@@ -82,14 +72,15 @@ ExecHash(HashState *node)
 		if (TupIsNull(slot))
 			break;
 		hashtable->hashNonEmpty = true;
+		/* We have to compute the hash value */
 		econtext->ecxt_innertuple = slot;
-		ExecHashTableInsert(hashtable, econtext, hashkeys);
-		ExecClearTuple(slot);
+		hashvalue = ExecHashGetHashValue(hashtable, econtext, hashkeys);
+		ExecHashTableInsert(hashtable, slot->val, hashvalue);
 	}
 
 	/*
 	 * Return the slot so that we have the tuple descriptor when we need
-	 * to save/restore them.  -Jeff 11 July 1991
+	 * to save/restore them.  -Jeff 11 July 1991  (XXX isn't this dead code?)
 	 */
 	return slot;
 }
@@ -198,7 +189,6 @@ ExecHashTableCreate(Hash *node, List *hashOperators)
 {
 	HashJoinTable hashtable;
 	Plan	   *outerNode;
-	int			totalbuckets;
 	int			nbuckets;
 	int			nbatch;
 	int			nkeys;
@@ -214,11 +204,10 @@ ExecHashTableCreate(Hash *node, List *hashOperators)
 	outerNode = outerPlan(node);
 
 	ExecChooseHashTableSize(outerNode->plan_rows, outerNode->plan_width,
-							&totalbuckets, &nbuckets, &nbatch);
+							&nbuckets, &nbatch);
 
 #ifdef HJDEBUG
-	printf("nbatch = %d, totalbuckets = %d, nbuckets = %d\n",
-		   nbatch, totalbuckets, nbuckets);
+	printf("nbatch = %d, nbuckets = %d\n", nbatch, nbuckets);
 #endif
 
 	/*
@@ -229,15 +218,17 @@ ExecHashTableCreate(Hash *node, List *hashOperators)
 	 */
 	hashtable = (HashJoinTable) palloc(sizeof(HashJoinTableData));
 	hashtable->nbuckets = nbuckets;
-	hashtable->totalbuckets = totalbuckets;
 	hashtable->buckets = NULL;
 	hashtable->nbatch = nbatch;
 	hashtable->curbatch = 0;
+	hashtable->nbatch_original = nbatch;
+	hashtable->nbatch_outstart = nbatch;
+	hashtable->growEnabled = true;
 	hashtable->hashNonEmpty = false;
 	hashtable->innerBatchFile = NULL;
 	hashtable->outerBatchFile = NULL;
-	hashtable->innerBatchSize = NULL;
-	hashtable->outerBatchSize = NULL;
+	hashtable->spaceUsed = 0;
+	hashtable->spaceAllowed = work_mem * 1024L;
 
 	/*
 	 * Get info about the hash functions to be used for each hash key.
@@ -277,7 +268,7 @@ ExecHashTableCreate(Hash *node, List *hashOperators)
 
 	oldcxt = MemoryContextSwitchTo(hashtable->hashCxt);
 
-	if (nbatch > 0)
+	if (nbatch > 1)
 	{
 		/*
 		 * allocate and initialize the file arrays in hashCxt
@@ -286,11 +277,7 @@ ExecHashTableCreate(Hash *node, List *hashOperators)
 			palloc0(nbatch * sizeof(BufFile *));
 		hashtable->outerBatchFile = (BufFile **)
 			palloc0(nbatch * sizeof(BufFile *));
-		hashtable->innerBatchSize = (long *)
-			palloc0(nbatch * sizeof(long));
-		hashtable->outerBatchSize = (long *)
-			palloc0(nbatch * sizeof(long));
-		/* The files will not be opened until later... */
+		/* The files will not be opened until needed... */
 	}
 
 	/*
@@ -312,42 +299,44 @@ ExecHashTableCreate(Hash *node, List *hashOperators)
  * Compute appropriate size for hashtable given the estimated size of the
  * relation to be hashed (number of rows and average row width).
  *
- * Caution: the input is only the planner's estimates, and so can't be
- * trusted too far.  Apply a healthy fudge factor.
- *
  * This is exported so that the planner's costsize.c can use it.
  */
 
 /* Target bucket loading (tuples per bucket) */
 #define NTUP_PER_BUCKET			10
-/* Fudge factor to allow for inaccuracy of input estimates */
-#define FUDGE_FAC				2.0
+
+/* Prime numbers that we like to use as nbuckets values */
+static const int hprimes[] = {
+	1033, 2063, 4111, 8219, 16417, 32779, 65539, 131111,
+	262151, 524341, 1048589, 2097211, 4194329, 8388619, 16777289, 33554473,
+	67108913, 134217773, 268435463, 536870951, 1073741831
+};
 
 void
 ExecChooseHashTableSize(double ntuples, int tupwidth,
-						int *virtualbuckets,
-						int *physicalbuckets,
+						int *numbuckets,
 						int *numbatches)
 {
 	int			tupsize;
 	double		inner_rel_bytes;
 	long		hash_table_bytes;
-	double		dtmp;
 	int			nbatch;
 	int			nbuckets;
-	int			totalbuckets;
-	int			bucketsize;
+	int			i;
 
 	/* Force a plausible relation size if no info */
 	if (ntuples <= 0.0)
 		ntuples = 1000.0;
 
 	/*
-	 * Estimate tupsize based on footprint of tuple in hashtable... but
-	 * what about palloc overhead?
+	 * Estimate tupsize based on footprint of tuple in hashtable... note
+	 * this does not allow for any palloc overhead.  The manipulations of
+	 * spaceUsed don't count palloc overhead either.
 	 */
-	tupsize = MAXALIGN(tupwidth) + MAXALIGN(sizeof(HashJoinTupleData));
-	inner_rel_bytes = ntuples * tupsize * FUDGE_FAC;
+	tupsize = MAXALIGN(sizeof(HashJoinTupleData)) +
+		MAXALIGN(sizeof(HeapTupleHeaderData)) +
+		MAXALIGN(tupwidth);
+	inner_rel_bytes = ntuples * tupsize;
 
 	/*
 	 * Target in-memory hashtable size is work_mem kilobytes.
@@ -355,73 +344,57 @@ ExecChooseHashTableSize(double ntuples, int tupwidth,
 	hash_table_bytes = work_mem * 1024L;
 
 	/*
-	 * Count the number of hash buckets we want for the whole relation,
-	 * for an average bucket load of NTUP_PER_BUCKET (per virtual
-	 * bucket!).  It has to fit in an int, however.
-	 */
-	dtmp = ceil(ntuples * FUDGE_FAC / NTUP_PER_BUCKET);
-	if (dtmp < INT_MAX)
-		totalbuckets = (int) dtmp;
-	else
-		totalbuckets = INT_MAX;
-	if (totalbuckets <= 0)
-		totalbuckets = 1;
-
-	/*
-	 * Count the number of buckets we think will actually fit in the
-	 * target memory size, at a loading of NTUP_PER_BUCKET (physical
-	 * buckets). NOTE: FUDGE_FAC here determines the fraction of the
-	 * hashtable space reserved to allow for nonuniform distribution of
-	 * hash values. Perhaps this should be a different number from the
-	 * other uses of FUDGE_FAC, but since we have no real good way to pick
-	 * either one...
+	 * Set nbuckets to achieve an average bucket load of NTUP_PER_BUCKET when
+	 * memory is filled.  Set nbatch to the smallest power of 2 that appears
+	 * sufficient.
 	 */
-	bucketsize = NTUP_PER_BUCKET * tupsize;
-	nbuckets = (int) (hash_table_bytes / (bucketsize * FUDGE_FAC));
-	if (nbuckets <= 0)
-		nbuckets = 1;
-
-	if (totalbuckets <= nbuckets)
+	if (inner_rel_bytes > hash_table_bytes)
 	{
-		/*
-		 * We have enough space, so no batching.  In theory we could even
-		 * reduce nbuckets, but since that could lead to poor behavior if
-		 * estimated ntuples is much less than reality, it seems better to
-		 * make more buckets instead of fewer.
-		 */
-		totalbuckets = nbuckets;
-		nbatch = 0;
+		/* We'll need multiple batches */
+		long	lbuckets;
+		double	dbatch;
+		int		minbatch;
+
+		lbuckets = (hash_table_bytes / tupsize) / NTUP_PER_BUCKET;
+		lbuckets = Min(lbuckets, INT_MAX);
+		nbuckets = (int) lbuckets;
+
+		dbatch = ceil(inner_rel_bytes / hash_table_bytes);
+		dbatch = Min(dbatch, INT_MAX/2);
+		minbatch = (int) dbatch;
+		nbatch = 2;
+		while (nbatch < minbatch)
+			nbatch <<= 1;
 	}
 	else
 	{
-		/*
-		 * Need to batch; compute how many batches we want to use. Note
-		 * that nbatch doesn't have to have anything to do with the ratio
-		 * 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.
-		 */
-		dtmp = ceil((inner_rel_bytes - hash_table_bytes) /
-					hash_table_bytes);
-		if (dtmp < INT_MAX)
-			nbatch = (int) dtmp;
-		else
-			nbatch = INT_MAX;
-		if (nbatch <= 0)
-			nbatch = 1;
+		/* We expect the hashtable to fit in memory */
+		double	dbuckets;
+
+		dbuckets = ceil(ntuples / NTUP_PER_BUCKET);
+		dbuckets = Min(dbuckets, INT_MAX);
+		nbuckets = (int) dbuckets;
+
+		nbatch = 1;
 	}
 
 	/*
-	 * Now, totalbuckets is the number of (virtual) hashbuckets for the
-	 * whole relation, and nbuckets is the number of physical hashbuckets
-	 * we will use in the first pass.  Data falling into the first
-	 * nbuckets virtual hashbuckets gets handled in the first pass;
-	 * everything else gets divided into nbatch batches to be processed in
-	 * additional passes.
+	 * We want nbuckets to be prime so as to avoid having bucket and batch
+	 * numbers depend on only some bits of the hash code.  Choose the next
+	 * larger prime from the list in hprimes[].  (This also enforces that
+	 * nbuckets is not very small, by the simple expedient of not putting
+	 * any very small entries in hprimes[].)
 	 */
-	*virtualbuckets = totalbuckets;
-	*physicalbuckets = nbuckets;
+	for (i = 0; i < (int) lengthof(hprimes); i++)
+	{
+		if (hprimes[i] >= nbuckets)
+		{
+			nbuckets = hprimes[i];
+			break;
+		}
+	}
+
+	*numbuckets = nbuckets;
 	*numbatches = nbatch;
 }
 
@@ -437,8 +410,12 @@ ExecHashTableDestroy(HashJoinTable hashtable)
 {
 	int			i;
 
-	/* Make sure all the temp files are closed */
-	for (i = 0; i < hashtable->nbatch; i++)
+	/*
+	 * Make sure all the temp files are closed.  We skip batch 0, since it
+	 * can't have any temp files (and the arrays might not even exist if
+	 * nbatch is only 1).
+	 */
+	for (i = 1; i < hashtable->nbatch; i++)
 	{
 		if (hashtable->innerBatchFile[i])
 			BufFileClose(hashtable->innerBatchFile[i]);
@@ -453,27 +430,159 @@ ExecHashTableDestroy(HashJoinTable hashtable)
 	pfree(hashtable);
 }
 
-/* ----------------------------------------------------------------
- *		ExecHashTableInsert
- *
+/*
+ * ExecHashIncreaseNumBatches
+ *		increase the original number of batches in order to reduce
+ *		current memory consumption
+ */
+static void
+ExecHashIncreaseNumBatches(HashJoinTable hashtable)
+{
+	int			oldnbatch = hashtable->nbatch;
+	int			curbatch = hashtable->curbatch;
+	int			nbatch;
+	int			i;
+	MemoryContext oldcxt;
+	long		ninmemory;
+	long		nfreed;
+
+	/* do nothing if we've decided to shut off growth */
+	if (!hashtable->growEnabled)
+		return;
+
+	/* safety check to avoid overflow */
+	if (oldnbatch > INT_MAX/2)
+		return;
+
+	nbatch = oldnbatch * 2;
+	Assert(nbatch > 1);
+
+#ifdef HJDEBUG
+	printf("Increasing nbatch to %d because space = %lu\n",
+		   nbatch, (unsigned long) hashtable->spaceUsed);
+#endif
+
+	oldcxt = MemoryContextSwitchTo(hashtable->hashCxt);
+
+	if (hashtable->innerBatchFile == NULL)
+	{
+		/* we had no file arrays before */
+		hashtable->innerBatchFile = (BufFile **)
+			palloc0(nbatch * sizeof(BufFile *));
+		hashtable->outerBatchFile = (BufFile **)
+			palloc0(nbatch * sizeof(BufFile *));
+	}
+	else
+	{
+		/* enlarge arrays and zero out added entries */
+		hashtable->innerBatchFile = (BufFile **)
+			repalloc(hashtable->innerBatchFile, nbatch * sizeof(BufFile *));
+		hashtable->outerBatchFile = (BufFile **)
+			repalloc(hashtable->outerBatchFile, nbatch * sizeof(BufFile *));
+		MemSet(hashtable->innerBatchFile + oldnbatch, 0,
+			   (nbatch - oldnbatch) * sizeof(BufFile *));
+		MemSet(hashtable->outerBatchFile + oldnbatch, 0,
+			   (nbatch - oldnbatch) * sizeof(BufFile *));
+	}
+
+	MemoryContextSwitchTo(oldcxt);
+
+	hashtable->nbatch = nbatch;
+
+	/*
+	 * Scan through the existing hash table entries and dump out any
+	 * that are no longer of the current batch.
+	 */
+	ninmemory = nfreed = 0;
+
+	for (i = 0; i < hashtable->nbuckets; i++)
+	{
+		HashJoinTuple prevtuple;
+		HashJoinTuple tuple;
+
+		prevtuple = NULL;
+		tuple = hashtable->buckets[i];
+
+		while (tuple != NULL)
+		{
+			/* save link in case we delete */
+			HashJoinTuple nexttuple = tuple->next;
+			int			bucketno;
+			int			batchno;
+
+			ninmemory++;
+			ExecHashGetBucketAndBatch(hashtable, tuple->hashvalue,
+									  &bucketno, &batchno);
+			Assert(bucketno == i);
+			if (batchno == curbatch)
+			{
+				/* keep tuple */
+				prevtuple = tuple;
+			}
+			else
+			{
+				/* dump it out */
+				Assert(batchno > curbatch);
+				ExecHashJoinSaveTuple(&tuple->htup, tuple->hashvalue,
+									  &hashtable->innerBatchFile[batchno]);
+				/* and remove from hash table */
+				if (prevtuple)
+					prevtuple->next = nexttuple;
+				else
+					hashtable->buckets[i] = nexttuple;
+				/* prevtuple doesn't change */
+				hashtable->spaceUsed -=
+					MAXALIGN(sizeof(HashJoinTupleData)) + tuple->htup.t_len;
+				pfree(tuple);
+				nfreed++;
+			}
+
+			tuple = nexttuple;
+		}
+	}
+
+#ifdef HJDEBUG
+	printf("Freed %ld of %ld tuples, space now %lu\n",
+		   nfreed, ninmemory, (unsigned long) hashtable->spaceUsed);
+#endif
+
+	/*
+	 * If we dumped out either all or none of the tuples in the table,
+	 * disable further expansion of nbatch.  This situation implies that
+	 * we have enough tuples of identical hashvalues to overflow spaceAllowed.
+	 * Increasing nbatch will not fix it since there's no way to subdivide
+	 * the group any more finely.
+	 * We have to just gut it out and hope the server has enough RAM.
+	 */
+	if (nfreed == 0 || nfreed == ninmemory)
+	{
+		hashtable->growEnabled = false;
+#ifdef HJDEBUG
+		printf("Disabling further increase of nbatch\n");
+#endif
+	}
+}
+
+/*
+ * ExecHashTableInsert
  *		insert a tuple into the hash table depending on the hash value
- *		it may just go to a tmp file for other batches
- * ----------------------------------------------------------------
+ *		it may just go to a temp file for later batches
  */
 void
 ExecHashTableInsert(HashJoinTable hashtable,
-					ExprContext *econtext,
-					List *hashkeys)
+					HeapTuple tuple,
+					uint32 hashvalue)
 {
-	int			bucketno = ExecHashGetBucket(hashtable, econtext, hashkeys);
-	int			batchno = ExecHashGetBatch(bucketno, hashtable);
-	TupleTableSlot *slot = econtext->ecxt_innertuple;
-	HeapTuple	heapTuple = slot->val;
+	int			bucketno;
+	int			batchno;
+
+	ExecHashGetBucketAndBatch(hashtable, hashvalue,
+							  &bucketno, &batchno);
 
 	/*
-	 * decide whether to put the tuple in the hash table or a tmp file
+	 * decide whether to put the tuple in the hash table or a temp file
 	 */
-	if (batchno < 0)
+	if (batchno == hashtable->curbatch)
 	{
 		/*
 		 * put the tuple in hash table
@@ -481,45 +590,50 @@ ExecHashTableInsert(HashJoinTable hashtable,
 		HashJoinTuple hashTuple;
 		int			hashTupleSize;
 
-		hashTupleSize = MAXALIGN(sizeof(*hashTuple)) + heapTuple->t_len;
+		hashTupleSize = MAXALIGN(sizeof(HashJoinTupleData)) + tuple->t_len;
 		hashTuple = (HashJoinTuple) MemoryContextAlloc(hashtable->batchCxt,
 													   hashTupleSize);
+		hashTuple->hashvalue = hashvalue;
 		memcpy((char *) &hashTuple->htup,
-			   (char *) heapTuple,
+			   (char *) tuple,
 			   sizeof(hashTuple->htup));
 		hashTuple->htup.t_datamcxt = hashtable->batchCxt;
 		hashTuple->htup.t_data = (HeapTupleHeader)
-			(((char *) hashTuple) + MAXALIGN(sizeof(*hashTuple)));
+			(((char *) hashTuple) + MAXALIGN(sizeof(HashJoinTupleData)));
 		memcpy((char *) hashTuple->htup.t_data,
-			   (char *) heapTuple->t_data,
-			   heapTuple->t_len);
+			   (char *) tuple->t_data,
+			   tuple->t_len);
 		hashTuple->next = hashtable->buckets[bucketno];
 		hashtable->buckets[bucketno] = hashTuple;
+		hashtable->spaceUsed += hashTupleSize;
+		if (hashtable->spaceUsed > hashtable->spaceAllowed)
+			ExecHashIncreaseNumBatches(hashtable);
 	}
 	else
 	{
 		/*
-		 * put the tuple into a tmp file for later batches
+		 * put the tuple into a temp file for later batches
 		 */
-		hashtable->innerBatchSize[batchno]++;
-		ExecHashJoinSaveTuple(heapTuple,
-							  hashtable->innerBatchFile[batchno]);
+		Assert(batchno > hashtable->curbatch);
+		ExecHashJoinSaveTuple(tuple, hashvalue,
+							  &hashtable->innerBatchFile[batchno]);
 	}
 }
 
-/* ----------------------------------------------------------------
- *		ExecHashGetBucket
+/*
+ * ExecHashGetHashValue
+ *		Compute the hash value for a tuple
  *
- *		Get the hash value for a tuple
- * ----------------------------------------------------------------
+ * The tuple to be tested must be in either econtext->ecxt_outertuple or
+ * econtext->ecxt_innertuple.  Vars in the hashkeys expressions reference
+ * either OUTER or INNER.
  */
-int
-ExecHashGetBucket(HashJoinTable hashtable,
-				  ExprContext *econtext,
-				  List *hashkeys)
+uint32
+ExecHashGetHashValue(HashJoinTable hashtable,
+					 ExprContext *econtext,
+					 List *hashkeys)
 {
 	uint32		hashkey = 0;
-	int			bucketno;
 	ListCell   *hk;
 	int			i = 0;
 	MemoryContext oldContext;
@@ -561,51 +675,63 @@ ExecHashGetBucket(HashJoinTable hashtable,
 		i++;
 	}
 
-	bucketno = hashkey % (uint32) hashtable->totalbuckets;
-
-#ifdef HJDEBUG
-	if (bucketno >= hashtable->nbuckets)
-		printf("hash(%u) = %d SAVED\n", hashkey, bucketno);
-	else
-		printf("hash(%u) = %d\n", hashkey, bucketno);
-#endif
-
 	MemoryContextSwitchTo(oldContext);
 
-	return bucketno;
+	return hashkey;
 }
 
-/* ----------------------------------------------------------------
- *		ExecHashGetBatch
+/*
+ * ExecHashGetBucketAndBatch
+ *		Determine the bucket number and batch number for a hash value
  *
- *		determine the batch number for a bucketno
+ * Note: on-the-fly increases of nbatch must not change the bucket number
+ * for a given hash code (since we don't move tuples to different hash
+ * chains), and must only cause the batch number to remain the same or
+ * increase.  Our algorithm is
+ *		bucketno = hashvalue MOD nbuckets
+ *		batchno = (hashvalue DIV nbuckets) MOD nbatch
+ * where nbuckets should preferably be prime so that all bits of the
+ * hash value can affect both bucketno and batchno.
+ * nbuckets doesn't change over the course of the join.
  *
- * Returns -1 if bucket belongs to initial (or current) batch,
- * else 0..nbatch-1 corresponding to external batch file number for bucket.
- * ----------------------------------------------------------------
+ * nbatch is always a power of 2; we increase it only by doubling it.  This
+ * effectively adds one more bit to the top of the batchno.
  */
-int
-ExecHashGetBatch(int bucketno, HashJoinTable hashtable)
+void
+ExecHashGetBucketAndBatch(HashJoinTable hashtable,
+						  uint32 hashvalue,
+						  int *bucketno,
+						  int *batchno)
 {
-	if (bucketno < hashtable->nbuckets)
-		return -1;
+	uint32	nbuckets = (uint32) hashtable->nbuckets;
+	uint32	nbatch = (uint32) hashtable->nbatch;
 
-	return (bucketno - hashtable->nbuckets) % hashtable->nbatch;
+	if (nbatch > 1)
+	{
+		*bucketno = hashvalue % nbuckets;
+		*batchno = (hashvalue / nbuckets) % nbatch;
+	}
+	else
+	{
+		*bucketno = hashvalue % nbuckets;
+		*batchno = 0;
+	}
 }
 
-/* ----------------------------------------------------------------
- *		ExecScanHashBucket
+/*
+ * ExecScanHashBucket
+ *		scan a hash bucket for matches to the current outer tuple
  *
- *		scan a hash bucket of matches
- * ----------------------------------------------------------------
+ * The current outer tuple must be stored in econtext->ecxt_outertuple.
  */
 HeapTuple
 ExecScanHashBucket(HashJoinState *hjstate,
-				   List *hjclauses,
 				   ExprContext *econtext)
 {
+	List	   *hjclauses = hjstate->hashclauses;
 	HashJoinTable hashtable = hjstate->hj_HashTable;
 	HashJoinTuple hashTuple = hjstate->hj_CurTuple;
+	uint32		hashvalue = hjstate->hj_CurHashValue;
 
 	/*
 	 * hj_CurTuple is NULL to start scanning a new bucket, or the address
@@ -618,23 +744,26 @@ ExecScanHashBucket(HashJoinState *hjstate,
 
 	while (hashTuple != NULL)
 	{
-		HeapTuple	heapTuple = &hashTuple->htup;
-		TupleTableSlot *inntuple;
-
-		/* insert hashtable's tuple into exec slot so ExecQual sees it */
-		inntuple = ExecStoreTuple(heapTuple,	/* tuple to store */
-								  hjstate->hj_HashTupleSlot,	/* slot */
-								  InvalidBuffer,
-								  false);		/* do not pfree this tuple */
-		econtext->ecxt_innertuple = inntuple;
-
-		/* reset temp memory each time to avoid leaks from qual expression */
-		ResetExprContext(econtext);
-
-		if (ExecQual(hjclauses, econtext, false))
+		if (hashTuple->hashvalue == hashvalue)
 		{
-			hjstate->hj_CurTuple = hashTuple;
-			return heapTuple;
+			HeapTuple	heapTuple = &hashTuple->htup;
+			TupleTableSlot *inntuple;
+
+			/* insert hashtable's tuple into exec slot so ExecQual sees it */
+			inntuple = ExecStoreTuple(heapTuple,
+									  hjstate->hj_HashTupleSlot,
+									  InvalidBuffer,
+									  false);	/* do not pfree */
+			econtext->ecxt_innertuple = inntuple;
+
+			/* reset temp memory each time to avoid leaks from qual expr */
+			ResetExprContext(econtext);
+
+			if (ExecQual(hjclauses, econtext, false))
+			{
+				hjstate->hj_CurTuple = hashTuple;
+				return heapTuple;
+			}
 		}
 
 		hashTuple = hashTuple->next;
@@ -646,17 +775,13 @@ ExecScanHashBucket(HashJoinState *hjstate,
 	return NULL;
 }
 
-/* ----------------------------------------------------------------
- *		ExecHashTableReset
+/*
+ * ExecHashTableReset
  *
  *		reset hash table header for new batch
- *
- *		ntuples is the number of tuples in the inner relation's batch
- *		(which we currently don't actually use...)
- * ----------------------------------------------------------------
  */
 void
-ExecHashTableReset(HashJoinTable hashtable, long ntuples)
+ExecHashTableReset(HashJoinTable hashtable)
 {
 	MemoryContext oldcxt;
 	int			nbuckets = hashtable->nbuckets;
@@ -668,22 +793,12 @@ ExecHashTableReset(HashJoinTable hashtable, long ntuples)
 	MemoryContextReset(hashtable->batchCxt);
 	oldcxt = MemoryContextSwitchTo(hashtable->batchCxt);
 
-	/*
-	 * We still use the same number of physical buckets as in the first
-	 * pass. (It could be different; but we already decided how many
-	 * buckets would be appropriate for the allowed memory, so stick with
-	 * that number.) We MUST set totalbuckets to equal nbuckets, because
-	 * from now on no tuples will go out to temp files; there are no more
-	 * virtual buckets, only real buckets.	(This implies that tuples will
-	 * go into different bucket numbers than they did on the first pass,
-	 * but that's OK.)
-	 */
-	hashtable->totalbuckets = nbuckets;
-
 	/* Reallocate and reinitialize the hash bucket headers. */
 	hashtable->buckets = (HashJoinTuple *)
 		palloc0(nbuckets * sizeof(HashJoinTuple));
 
+	hashtable->spaceUsed = 0;
+
 	MemoryContextSwitchTo(oldcxt);
 }
 

src/backend/executor/nodeHashjoin.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeHashjoin.c,v 1.67 2004/12/31 21:59:45 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeHashjoin.c,v 1.68 2005/03/06 22:15:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -16,16 +16,19 @@
 #include "postgres.h"
 
 #include "executor/executor.h"
+#include "executor/hashjoin.h"
 #include "executor/nodeHash.h"
 #include "executor/nodeHashjoin.h"
 #include "optimizer/clauses.h"
 #include "utils/memutils.h"
 
 
-static TupleTableSlot *ExecHashJoinOuterGetTuple(PlanState *node,
-						  HashJoinState *hjstate);
+static TupleTableSlot *ExecHashJoinOuterGetTuple(PlanState *outerNode,
+												 HashJoinState *hjstate,
+												 uint32 *hashvalue);
 static TupleTableSlot *ExecHashJoinGetSavedTuple(HashJoinState *hjstate,
 						  BufFile *file,
+						  uint32 *hashvalue,
 						  TupleTableSlot *tupleSlot);
 static int	ExecHashJoinNewBatch(HashJoinState *hjstate);
 
@@ -34,9 +37,9 @@ static int	ExecHashJoinNewBatch(HashJoinState *hjstate);
  *		ExecHashJoin
  *
  *		This function implements the Hybrid Hashjoin algorithm.
- *		recursive partitioning remains to be added.
- *		Note: the relation we build hash table on is the inner
- *			  the other one is outer.
+ *
+ *		Note: the relation we build hash table on is the "inner"
+ *			  the other one is "outer".
  * ----------------------------------------------------------------
  */
 TupleTableSlot *				/* return: a tuple or NULL */
@@ -45,8 +48,6 @@ ExecHashJoin(HashJoinState *node)
 	EState	   *estate;
 	PlanState  *outerNode;
 	HashState  *hashNode;
-	List	   *hjclauses;
-	List	   *outerkeys;
 	List	   *joinqual;
 	List	   *otherqual;
 	ScanDirection dir;
@@ -56,12 +57,12 @@ ExecHashJoin(HashJoinState *node)
 	HashJoinTable hashtable;
 	HeapTuple	curtuple;
 	TupleTableSlot *outerTupleSlot;
-	int			i;
+	uint32		hashvalue;
+	int			batchno;
 
 	/*
 	 * get information from HashJoin node
 	 */
-	hjclauses = node->hashclauses;
 	estate = node->js.ps.state;
 	joinqual = node->js.joinqual;
 	otherqual = node->js.ps.qual;
@@ -73,7 +74,6 @@ ExecHashJoin(HashJoinState *node)
 	 * get information from HashJoin state
 	 */
 	hashtable = node->hj_HashTable;
-	outerkeys = node->hj_OuterHashKeys;
 	econtext = node->js.ps.ps_ExprContext;
 
 	/*
@@ -111,12 +111,11 @@ ExecHashJoin(HashJoinState *node)
 	/*
 	 * if this is the first call, build the hash table for inner relation
 	 */
-	if (!node->hj_hashdone)
+	if (hashtable == NULL)
 	{
 		/*
 		 * create the hash table
 		 */
-		Assert(hashtable == NULL);
 		hashtable = ExecHashTableCreate((Hash *) hashNode->ps.plan,
 										node->hj_HashOperators);
 		node->hj_HashTable = hashtable;
@@ -139,13 +138,10 @@ ExecHashJoin(HashJoinState *node)
 		}
 
 		/*
-		 * Open temp files for outer batches, if needed. Note that file
-		 * buffers are palloc'd in regular executor context.
+		 * need to remember whether nbatch has increased since we began
+		 * scanning the outer relation
 		 */
-		for (i = 0; i < hashtable->nbatch; i++)
-			hashtable->outerBatchFile[i] = BufFileCreateTemp(false);
-
-		node->hj_hashdone = true;
+		hashtable->nbatch_outstart = hashtable->nbatch;
 	}
 
 	/*
@@ -159,7 +155,8 @@ ExecHashJoin(HashJoinState *node)
 		if (node->hj_NeedNewOuter)
 		{
 			outerTupleSlot = ExecHashJoinOuterGetTuple(outerNode,
-													   node);
+													   node,
+													   &hashvalue);
 			if (TupIsNull(outerTupleSlot))
 			{
 				/* end of join */
@@ -175,32 +172,26 @@ ExecHashJoin(HashJoinState *node)
 			 * now we have an outer tuple, find the corresponding bucket
 			 * for this tuple from the hash table
 			 */
-			node->hj_CurBucketNo = ExecHashGetBucket(hashtable, econtext,
-													 outerkeys);
+			node->hj_CurHashValue = hashvalue;
+			ExecHashGetBucketAndBatch(hashtable, hashvalue,
+									  &node->hj_CurBucketNo, &batchno);
 			node->hj_CurTuple = NULL;
 
 			/*
 			 * Now we've got an outer tuple and the corresponding hash
 			 * bucket, but this tuple may not belong to the current batch.
-			 * This need only be checked in the first pass.
 			 */
-			if (hashtable->curbatch == 0)
+			if (batchno != hashtable->curbatch)
 			{
-				int			batchno = ExecHashGetBatch(node->hj_CurBucketNo,
-													   hashtable);
-
-				if (batchno >= 0)
-				{
-					/*
-					 * Need to postpone this outer tuple to a later batch.
-					 * Save it in the corresponding outer-batch file.
-					 */
-					hashtable->outerBatchSize[batchno]++;
-					ExecHashJoinSaveTuple(outerTupleSlot->val,
-									 hashtable->outerBatchFile[batchno]);
-					node->hj_NeedNewOuter = true;
-					continue;	/* loop around for a new outer tuple */
-				}
+				/*
+				 * Need to postpone this outer tuple to a later batch.
+				 * Save it in the corresponding outer-batch file.
+				 */
+				Assert(batchno > hashtable->curbatch);
+				ExecHashJoinSaveTuple(outerTupleSlot->val, hashvalue,
+									  &hashtable->outerBatchFile[batchno]);
+				node->hj_NeedNewOuter = true;
+				continue;	/* loop around for a new outer tuple */
 			}
 		}
 
@@ -209,9 +200,7 @@ ExecHashJoin(HashJoinState *node)
 		 */
 		for (;;)
 		{
-			curtuple = ExecScanHashBucket(node,
-										  hjclauses,
-										  econtext);
+			curtuple = ExecScanHashBucket(node, econtext);
 			if (curtuple == NULL)
 				break;			/* out of matches */
 
@@ -412,10 +401,9 @@ ExecInitHashJoin(HashJoin *node, EState *estate)
 	/*
 	 * initialize hash-specific info
 	 */
-
-	hjstate->hj_hashdone = false;
 	hjstate->hj_HashTable = NULL;
 
+	hjstate->hj_CurHashValue = 0;
 	hjstate->hj_CurBucketNo = 0;
 	hjstate->hj_CurTuple = NULL;
 
@@ -499,17 +487,21 @@ ExecEndHashJoin(HashJoinState *node)
 	ExecEndNode(innerPlanState(node));
 }
 
-/* ----------------------------------------------------------------
- *		ExecHashJoinOuterGetTuple
+/*
+ * ExecHashJoinOuterGetTuple
  *
  *		get the next outer tuple for hashjoin: either by
- *		executing a plan node as in the first pass, or from
- *		the tmp files for the hashjoin batches.
- * ----------------------------------------------------------------
+ *		executing a plan node in the first pass, or from
+ *		the temp files for the hashjoin batches.
+ *
+ * Returns a null slot if no more outer tuples.  On success, the tuple's
+ * hash value is stored at *hashvalue --- this is either originally computed,
+ * or re-read from the temp file.
  */
-
 static TupleTableSlot *
-ExecHashJoinOuterGetTuple(PlanState *node, HashJoinState *hjstate)
+ExecHashJoinOuterGetTuple(PlanState *outerNode,
+						  HashJoinState *hjstate,
+						  uint32 *hashvalue)
 {
 	HashJoinTable hashtable = hjstate->hj_HashTable;
 	int			curbatch = hashtable->curbatch;
@@ -517,9 +509,20 @@ ExecHashJoinOuterGetTuple(PlanState *node, HashJoinState *hjstate)
 
 	if (curbatch == 0)
 	{							/* if it is the first pass */
-		slot = ExecProcNode(node);
+		slot = ExecProcNode(outerNode);
 		if (!TupIsNull(slot))
+		{
+			/*
+			 * We have to compute the tuple's hash value.
+			 */
+			ExprContext *econtext = hjstate->js.ps.ps_ExprContext;
+
+			econtext->ecxt_outertuple = slot;
+			*hashvalue = ExecHashGetHashValue(hashtable, econtext,
+											  hjstate->hj_OuterHashKeys);
+
 			return slot;
+		}
 
 		/*
 		 * We have just reached the end of the first pass. Try to switch
@@ -530,12 +533,14 @@ ExecHashJoinOuterGetTuple(PlanState *node, HashJoinState *hjstate)
 
 	/*
 	 * Try to read from a temp file. Loop allows us to advance to new
-	 * batch as needed.
+	 * batches as needed.  NOTE: nbatch could increase inside
+	 * ExecHashJoinNewBatch, so don't try to optimize this loop.
 	 */
-	while (curbatch <= hashtable->nbatch)
+	while (curbatch < hashtable->nbatch)
 	{
 		slot = ExecHashJoinGetSavedTuple(hjstate,
-								 hashtable->outerBatchFile[curbatch - 1],
+										 hashtable->outerBatchFile[curbatch],
+										 hashvalue,
 										 hjstate->hj_OuterTupleSlot);
 		if (!TupIsNull(slot))
 			return slot;
@@ -546,164 +551,223 @@ ExecHashJoinOuterGetTuple(PlanState *node, HashJoinState *hjstate)
 	return NULL;
 }
 
-/* ----------------------------------------------------------------
- *		ExecHashJoinGetSavedTuple
- *
- *		read the next tuple from a tmp file
- * ----------------------------------------------------------------
- */
-
-static TupleTableSlot *
-ExecHashJoinGetSavedTuple(HashJoinState *hjstate,
-						  BufFile *file,
-						  TupleTableSlot *tupleSlot)
-{
-	HeapTupleData htup;
-	size_t		nread;
-	HeapTuple	heapTuple;
-
-	nread = BufFileRead(file, (void *) &htup, sizeof(HeapTupleData));
-	if (nread == 0)
-		return NULL;			/* end of file */
-	if (nread != sizeof(HeapTupleData))
-		ereport(ERROR,
-				(errcode_for_file_access(),
-			errmsg("could not read from hash-join temporary file: %m")));
-	heapTuple = palloc(HEAPTUPLESIZE + htup.t_len);
-	memcpy((char *) heapTuple, (char *) &htup, sizeof(HeapTupleData));
-	heapTuple->t_datamcxt = CurrentMemoryContext;
-	heapTuple->t_data = (HeapTupleHeader)
-		((char *) heapTuple + HEAPTUPLESIZE);
-	nread = BufFileRead(file, (void *) heapTuple->t_data, htup.t_len);
-	if (nread != (size_t) htup.t_len)
-		ereport(ERROR,
-				(errcode_for_file_access(),
-			errmsg("could not read from hash-join temporary file: %m")));
-	return ExecStoreTuple(heapTuple, tupleSlot, InvalidBuffer, true);
-}
-
-/* ----------------------------------------------------------------
- *		ExecHashJoinNewBatch
- *
+/*
+ * ExecHashJoinNewBatch
  *		switch to a new hashjoin batch
- * ----------------------------------------------------------------
+ *
+ * Returns the number of the new batch (1..nbatch-1), or nbatch if no more.
+ * We will never return a batch number that has an empty outer batch file.
  */
 static int
 ExecHashJoinNewBatch(HashJoinState *hjstate)
 {
 	HashJoinTable hashtable = hjstate->hj_HashTable;
-	int			nbatch = hashtable->nbatch;
-	int			newbatch = hashtable->curbatch + 1;
-	long	   *innerBatchSize = hashtable->innerBatchSize;
-	long	   *outerBatchSize = hashtable->outerBatchSize;
+	int			nbatch;
+	int			curbatch;
 	BufFile    *innerFile;
 	TupleTableSlot *slot;
-	ExprContext *econtext;
-	List	   *innerhashkeys;
+	uint32		hashvalue;
 
-	if (newbatch > 1)
+start_over:
+	nbatch = hashtable->nbatch;
+	curbatch = hashtable->curbatch;
+
+	if (curbatch > 0)
 	{
 		/*
 		 * We no longer need the previous outer batch file; close it right
 		 * away to free disk space.
 		 */
-		BufFileClose(hashtable->outerBatchFile[newbatch - 2]);
-		hashtable->outerBatchFile[newbatch - 2] = NULL;
+		if (hashtable->outerBatchFile[curbatch])
+			BufFileClose(hashtable->outerBatchFile[curbatch]);
+		hashtable->outerBatchFile[curbatch] = NULL;
 	}
 
 	/*
-	 * Normally we can skip over any batches that are empty on either side
-	 * --- but for JOIN_LEFT, can only skip when left side is empty.
-	 * Release associated temp files right away.
+	 * We can always skip over any batches that are completely empty on both
+	 * sides.  We can sometimes skip over batches that are empty on only one
+	 * side, but there are exceptions:
+	 *
+	 * 1. In a LEFT JOIN, we have to process outer batches even if the
+	 * inner batch is empty.
+	 *
+	 * 2. If we have increased nbatch since the initial estimate, we have
+	 * to scan inner batches since they might contain tuples that need to
+	 * be reassigned to later inner batches.
+	 *
+	 * 3. Similarly, if we have increased nbatch since starting the outer
+	 * scan, we have to rescan outer batches in case they contain tuples
+	 * that need to be reassigned.
 	 */
-	while (newbatch <= nbatch &&
-		   (outerBatchSize[newbatch - 1] == 0L ||
-			(innerBatchSize[newbatch - 1] == 0L &&
-			 hjstate->js.jointype != JOIN_LEFT)))
+	curbatch++;
+	while (curbatch < nbatch &&
+		   (hashtable->outerBatchFile[curbatch] == NULL ||
+			hashtable->innerBatchFile[curbatch] == NULL))
 	{
-		BufFileClose(hashtable->innerBatchFile[newbatch - 1]);
-		hashtable->innerBatchFile[newbatch - 1] = NULL;
-		BufFileClose(hashtable->outerBatchFile[newbatch - 1]);
-		hashtable->outerBatchFile[newbatch - 1] = NULL;
-		newbatch++;
+		if (hashtable->outerBatchFile[curbatch] &&
+			hjstate->js.jointype == JOIN_LEFT)
+			break;				/* must process due to rule 1 */
+		if (hashtable->innerBatchFile[curbatch] &&
+			nbatch != hashtable->nbatch_original)
+			break;				/* must process due to rule 2 */
+		if (hashtable->outerBatchFile[curbatch] &&
+			nbatch != hashtable->nbatch_outstart)
+			break;				/* must process due to rule 3 */
+		/* We can ignore this batch. */
+		/* Release associated temp files right away. */
+		if (hashtable->innerBatchFile[curbatch])
+			BufFileClose(hashtable->innerBatchFile[curbatch]);
+		hashtable->innerBatchFile[curbatch] = NULL;
+		if (hashtable->outerBatchFile[curbatch])
+			BufFileClose(hashtable->outerBatchFile[curbatch]);
+		hashtable->outerBatchFile[curbatch] = NULL;
+		curbatch++;
 	}
 
-	if (newbatch > nbatch)
-		return newbatch;		/* no more batches */
-
-	/*
-	 * Rewind inner and outer batch files for this batch, so that we can
-	 * start reading them.
-	 */
-	if (BufFileSeek(hashtable->outerBatchFile[newbatch - 1], 0, 0L, SEEK_SET))
-		ereport(ERROR,
-				(errcode_for_file_access(),
-			   errmsg("could not rewind hash-join temporary file: %m")));
+	if (curbatch >= nbatch)
+		return curbatch;		/* no more batches */
 
-	innerFile = hashtable->innerBatchFile[newbatch - 1];
-
-	if (BufFileSeek(innerFile, 0, 0L, SEEK_SET))
-		ereport(ERROR,
-				(errcode_for_file_access(),
-			   errmsg("could not rewind hash-join temporary file: %m")));
+	hashtable->curbatch = curbatch;
 
 	/*
-	 * Reload the hash table with the new inner batch
+	 * Reload the hash table with the new inner batch (which could be empty)
 	 */
-	ExecHashTableReset(hashtable, innerBatchSize[newbatch - 1]);
+	ExecHashTableReset(hashtable);
 
-	econtext = hjstate->js.ps.ps_ExprContext;
-	innerhashkeys = hjstate->hj_InnerHashKeys;
+	innerFile = hashtable->innerBatchFile[curbatch];
 
-	while ((slot = ExecHashJoinGetSavedTuple(hjstate,
-											 innerFile,
-											 hjstate->hj_HashTupleSlot))
-		   && !TupIsNull(slot))
+	if (innerFile != NULL)
 	{
-		econtext->ecxt_innertuple = slot;
-		ExecHashTableInsert(hashtable, econtext, innerhashkeys);
+		if (BufFileSeek(innerFile, 0, 0L, SEEK_SET))
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not rewind hash-join temporary file: %m")));
+
+		while ((slot = ExecHashJoinGetSavedTuple(hjstate,
+												 innerFile,
+												 &hashvalue,
+												 hjstate->hj_HashTupleSlot)))
+		{
+			/*
+			 * NOTE: some tuples may be sent to future batches.  Also,
+			 * it is possible for hashtable->nbatch to be increased here!
+			 */
+			ExecHashTableInsert(hashtable, slot->val, hashvalue);
+		}
+
+		/*
+		 * after we build the hash table, the inner batch file is no longer
+		 * needed
+		 */
+		BufFileClose(innerFile);
+		hashtable->innerBatchFile[curbatch] = NULL;
 	}
 
 	/*
-	 * after we build the hash table, the inner batch file is no longer
-	 * needed
+	 * If there's no outer batch file, advance to next batch.
 	 */
-	BufFileClose(innerFile);
-	hashtable->innerBatchFile[newbatch - 1] = NULL;
+	if (hashtable->outerBatchFile[curbatch] == NULL)
+		goto start_over;
 
-	hashtable->curbatch = newbatch;
-	return newbatch;
+	/*
+	 * Rewind outer batch file, so that we can start reading it.
+	 */
+	if (BufFileSeek(hashtable->outerBatchFile[curbatch], 0, 0L, SEEK_SET))
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not rewind hash-join temporary file: %m")));
+
+	return curbatch;
 }
 
-/* ----------------------------------------------------------------
- *		ExecHashJoinSaveTuple
+/*
+ * ExecHashJoinSaveTuple
+ *		save a tuple to a batch file.
  *
- *		save a tuple to a tmp file.
+ * The data recorded in the file for each tuple is its hash value,
+ * then an image of its HeapTupleData (with meaningless t_data pointer)
+ * followed by the HeapTupleHeader and tuple data.
  *
- * The data recorded in the file for each tuple is an image of its
- * HeapTupleData (with meaningless t_data pointer) followed by the
- * HeapTupleHeader and tuple data.
- * ----------------------------------------------------------------
+ * Note: it is important always to call this in the regular executor
+ * context, not in a shorter-lived context; else the temp file buffers
+ * will get messed up.
  */
-
 void
-ExecHashJoinSaveTuple(HeapTuple heapTuple,
-					  BufFile *file)
+ExecHashJoinSaveTuple(HeapTuple heapTuple, uint32 hashvalue,
+					  BufFile **fileptr)
 {
+	BufFile	   *file = *fileptr;
 	size_t		written;
 
+	if (file == NULL)
+	{
+		/* First write to this batch file, so open it. */
+		file = BufFileCreateTemp(false);
+		*fileptr = file;
+	}
+
+	written = BufFileWrite(file, (void *) &hashvalue, sizeof(uint32));
+	if (written != sizeof(uint32))
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not write to hash-join temporary file: %m")));
+
 	written = BufFileWrite(file, (void *) heapTuple, sizeof(HeapTupleData));
 	if (written != sizeof(HeapTupleData))
 		ereport(ERROR,
 				(errcode_for_file_access(),
-			 errmsg("could not write to hash-join temporary file: %m")));
+				 errmsg("could not write to hash-join temporary file: %m")));
+
 	written = BufFileWrite(file, (void *) heapTuple->t_data, heapTuple->t_len);
 	if (written != (size_t) heapTuple->t_len)
 		ereport(ERROR,
 				(errcode_for_file_access(),
-			 errmsg("could not write to hash-join temporary file: %m")));
+				 errmsg("could not write to hash-join temporary file: %m")));
 }
 
+/*
+ * ExecHashJoinGetSavedTuple
+ *		read the next tuple from a batch file.  Return NULL if no more.
+ *
+ * On success, *hashvalue is set to the tuple's hash value, and the tuple
+ * itself is stored in the given slot.
+ */
+static TupleTableSlot *
+ExecHashJoinGetSavedTuple(HashJoinState *hjstate,
+						  BufFile *file,
+						  uint32 *hashvalue,
+						  TupleTableSlot *tupleSlot)
+{
+	HeapTupleData htup;
+	size_t		nread;
+	HeapTuple	heapTuple;
+
+	nread = BufFileRead(file, (void *) hashvalue, sizeof(uint32));
+	if (nread == 0)
+		return NULL;			/* end of file */
+	if (nread != sizeof(uint32))
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not read from hash-join temporary file: %m")));
+	nread = BufFileRead(file, (void *) &htup, sizeof(HeapTupleData));
+	if (nread != sizeof(HeapTupleData))
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not read from hash-join temporary file: %m")));
+	heapTuple = palloc(HEAPTUPLESIZE + htup.t_len);
+	memcpy((char *) heapTuple, (char *) &htup, sizeof(HeapTupleData));
+	heapTuple->t_datamcxt = CurrentMemoryContext;
+	heapTuple->t_data = (HeapTupleHeader)
+		((char *) heapTuple + HEAPTUPLESIZE);
+	nread = BufFileRead(file, (void *) heapTuple->t_data, htup.t_len);
+	if (nread != (size_t) htup.t_len)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not read from hash-join temporary file: %m")));
+	return ExecStoreTuple(heapTuple, tupleSlot, InvalidBuffer, true);
+}
+
+
 void
 ExecReScanHashJoin(HashJoinState *node, ExprContext *exprCtxt)
 {
@@ -711,9 +775,8 @@ ExecReScanHashJoin(HashJoinState *node, ExprContext *exprCtxt)
 	 * If we haven't yet built the hash table then we can just return;
 	 * nothing done yet, so nothing to undo.
 	 */
-	if (!node->hj_hashdone)
+	if (node->hj_HashTable == NULL)
 		return;
-	Assert(node->hj_HashTable != NULL);
 
 	/*
 	 * In a multi-batch join, we currently have to do rescans the hard
@@ -722,7 +785,7 @@ ExecReScanHashJoin(HashJoinState *node, ExprContext *exprCtxt)
 	 * parameter change for the inner subnode, then we can just re-use the
 	 * existing hash table without rebuilding it.
 	 */
-	if (node->hj_HashTable->nbatch == 0 &&
+	if (node->hj_HashTable->nbatch == 1 &&
 		((PlanState *) node)->righttree->chgParam == NULL)
 	{
 		/* okay to reuse the hash table; needn't rescan inner, either */
@@ -730,7 +793,6 @@ ExecReScanHashJoin(HashJoinState *node, ExprContext *exprCtxt)
 	else
 	{
 		/* must destroy and rebuild hash table */
-		node->hj_hashdone = false;
 		ExecHashTableDestroy(node->hj_HashTable);
 		node->hj_HashTable = NULL;
 
@@ -743,6 +805,7 @@ ExecReScanHashJoin(HashJoinState *node, ExprContext *exprCtxt)
 	}
 
 	/* Always reset intra-tuple state */
+	node->hj_CurHashValue = 0;
 	node->hj_CurBucketNo = 0;
 	node->hj_CurTuple = NULL;
 

src/backend/optimizer/path/costsize.c

@@ -49,7 +49,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.137 2004/12/31 22:00:04 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.138 2005/03/06 22:15:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1074,9 +1074,9 @@ cost_hashjoin(HashPath *path, Query *root)
 	double		innerbytes = relation_byte_size(inner_path_rows,
 											  inner_path->parent->width);
 	int			num_hashclauses = list_length(hashclauses);
-	int			virtualbuckets;
-	int			physicalbuckets;
+	int			numbuckets;
 	int			numbatches;
+	double		virtualbuckets;
 	Selectivity innerbucketsize;
 	Selectivity joininfactor;
 	ListCell   *hcl;
@@ -1123,9 +1123,9 @@ cost_hashjoin(HashPath *path, Query *root)
 	/* Get hash table size that executor would use for inner relation */
 	ExecChooseHashTableSize(inner_path_rows,
 							inner_path->parent->width,
-							&virtualbuckets,
-							&physicalbuckets,
+							&numbuckets,
 							&numbatches);
+	virtualbuckets = (double) numbuckets * (double) numbatches;
 
 	/*
 	 * Determine bucketsize fraction for inner relation.  We use the
@@ -1196,13 +1196,13 @@ cost_hashjoin(HashPath *path, Query *root)
 	}
 
 	/*
-	 * if inner relation is too big then we will need to "batch" the join,
+	 * If inner relation is too big then we will need to "batch" the join,
 	 * which implies writing and reading most of the tuples to disk an
 	 * extra time.	Charge one cost unit per page of I/O (correct since it
 	 * should be nice and sequential...).  Writing the inner rel counts as
 	 * startup cost, all the rest as run cost.
 	 */
-	if (numbatches)
+	if (numbatches > 1)
 	{
 		double		outerpages = page_size(outer_path_rows,
 										   outer_path->parent->width);
@@ -1228,7 +1228,9 @@ cost_hashjoin(HashPath *path, Query *root)
 	 * The number of tuple comparisons needed is the number of outer
 	 * tuples times the typical number of tuples in a hash bucket, which
 	 * is the inner relation size times its bucketsize fraction.  At each
-	 * one, we need to evaluate the hashjoin quals.
+	 * one, we need to evaluate the hashjoin quals.  (Note: charging the
+	 * full qual eval cost at each tuple is pessimistic, since we don't
+	 * evaluate the quals unless the hash values match exactly.)
 	 */
 	startup_cost += hash_qual_cost.startup;
 	run_cost += hash_qual_cost.per_tuple *

src/backend/utils/adt/selfuncs.c

@@ -15,7 +15,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.171 2005/02/01 23:07:58 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.172 2005/03/06 22:15:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2154,7 +2154,7 @@ estimate_num_groups(Query *root, List *groupExprs, double input_rows)
  * inner rel is well-dispersed (or the alternatives seem much worse).
  */
 Selectivity
-estimate_hash_bucketsize(Query *root, Node *hashkey, int nbuckets)
+estimate_hash_bucketsize(Query *root, Node *hashkey, double nbuckets)
 {
 	VariableStatData vardata;
 	double		estfract,
@@ -2212,8 +2212,8 @@ estimate_hash_bucketsize(Query *root, Node *hashkey, int nbuckets)
 	 * the number of buckets is less than the expected number of distinct
 	 * values; otherwise it is 1/ndistinct.
 	 */
-	if (ndistinct > (double) nbuckets)
-		estfract = 1.0 / (double) nbuckets;
+	if (ndistinct > nbuckets)
+		estfract = 1.0 / nbuckets;
 	else
 		estfract = 1.0 / ndistinct;
 

src/include/executor/hashjoin.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/executor/hashjoin.h,v 1.34 2004/12/31 22:03:29 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/executor/hashjoin.h,v 1.35 2005/03/06 22:15:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -20,11 +20,12 @@
 /* ----------------------------------------------------------------
  *				hash-join hash table structures
  *
- * Each active hashjoin has a HashJoinTable control block which is
+ * Each active hashjoin has a HashJoinTable control block, which is
  * palloc'd in the executor's per-query context.  All other storage needed
  * for the hashjoin is kept in private memory contexts, two for each hashjoin.
  * This makes it easy and fast to release the storage when we don't need it
- * anymore.
+ * anymore.  (Exception: data associated with the temp files lives in the
+ * per-query context too, since we always call buffile.c in that context.)
  *
  * The hashtable contexts are made children of the per-query context, ensuring
  * that they will be discarded at end of statement even if the join is
@@ -35,40 +36,64 @@
  * "hashCxt", while storage that is only wanted for the current batch is
  * allocated in the "batchCxt".  By resetting the batchCxt at the end of
  * each batch, we free all the per-batch storage reliably and without tedium.
+ *
+ * During first scan of inner relation, we get its tuples from executor.
+ * If nbatch > 1 then tuples that don't belong in first batch get saved
+ * into inner-batch temp files. The same statements apply for the
+ * first scan of the outer relation, except we write tuples to outer-batch
+ * temp files.  After finishing the first scan, we do the following for
+ * each remaining batch:
+ *	1. Read tuples from inner batch file, load into hash buckets.
+ *	2. Read tuples from outer batch file, match to hash buckets and output.
+ *
+ * It is possible to increase nbatch on the fly if the in-memory hash table
+ * gets too big.  The hash-value-to-batch computation is arranged so that this
+ * can only cause a tuple to go into a later batch than previously thought,
+ * never into an earlier batch.  When we increase nbatch, we rescan the hash
+ * table and dump out any tuples that are now of a later batch to the correct
+ * inner batch file.  Subsequently, while reading either inner or outer batch
+ * files, we might find tuples that no longer belong to the current batch;
+ * if so, we just dump them out to the correct batch file.
  * ----------------------------------------------------------------
  */
 
+/* these are in nodes/execnodes.h: */
+/* typedef struct HashJoinTupleData *HashJoinTuple; */
+/* typedef struct HashJoinTableData *HashJoinTable; */
+
 typedef struct HashJoinTupleData
 {
-	struct HashJoinTupleData *next;		/* link to next tuple in same
-										 * bucket */
+	struct HashJoinTupleData *next;	/* link to next tuple in same bucket */
+	uint32		hashvalue;		/* tuple's hash code */
 	HeapTupleData htup;			/* tuple header */
 } HashJoinTupleData;
 
-typedef HashJoinTupleData *HashJoinTuple;
-
 typedef struct HashJoinTableData
 {
-	int			nbuckets;		/* buckets in use during this batch */
-	int			totalbuckets;	/* total number of (virtual) buckets */
-	HashJoinTuple *buckets;		/* buckets[i] is head of list of tuples */
+	int			nbuckets;		/* # buckets in the in-memory hash table */
+	/* buckets[i] is head of list of tuples in i'th in-memory bucket */
+	struct HashJoinTupleData **buckets;
 	/* buckets array is per-batch storage, as are all the tuples */
 
-	int			nbatch;			/* number of batches; 0 means 1-pass join */
-	int			curbatch;		/* current batch #, or 0 during 1st pass */
+	int			nbatch;			/* number of batches */
+	int			curbatch;		/* current batch #; 0 during 1st pass */
+
+	int			nbatch_original;	/* nbatch when we started inner scan */
+	int			nbatch_outstart;	/* nbatch when we started outer scan */
+
+	bool		growEnabled;	/* flag to shut off nbatch increases */
 
 	bool		hashNonEmpty;	/* did inner plan produce any rows? */
 
 	/*
-	 * all these arrays are allocated for the life of the hash join, but
-	 * only if nbatch > 0:
+	 * These arrays are allocated for the life of the hash join, but
+	 * only if nbatch > 1.  A file is opened only when we first write
+	 * a tuple into it (otherwise its pointer remains NULL).  Note that
+	 * the zero'th array elements never get used, since we will process
+	 * rather than dump out any tuples of batch zero.
 	 */
 	BufFile   **innerBatchFile; /* buffered virtual temp file per batch */
 	BufFile   **outerBatchFile; /* buffered virtual temp file per batch */
-	long	   *outerBatchSize; /* count of tuples in each outer batch
-								 * file */
-	long	   *innerBatchSize; /* count of tuples in each inner batch
-								 * file */
 
 	/*
 	 * Info about the datatype-specific hash functions for the datatypes
@@ -79,21 +104,11 @@ typedef struct HashJoinTableData
 	 */
 	FmgrInfo   *hashfunctions;	/* lookup data for hash functions */
 
-	/*
-	 * During 1st scan of inner relation, we get tuples from executor. If
-	 * nbatch > 0 then tuples that don't belong in first nbuckets logical
-	 * buckets get dumped into inner-batch temp files. The same statements
-	 * apply for the 1st scan of the outer relation, except we write
-	 * tuples to outer-batch temp files. If nbatch > 0 then we do the
-	 * following for each batch: 1. Read tuples from inner batch file,
-	 * load into hash buckets. 2. Read tuples from outer batch file, match
-	 * to hash buckets and output.
-	 */
+	Size		spaceUsed;		/* memory space currently used by tuples */
+	Size		spaceAllowed;	/* upper limit for space used */
 
 	MemoryContext hashCxt;		/* context for whole-hash-join storage */
 	MemoryContext batchCxt;		/* context for this-batch-only storage */
 } HashJoinTableData;
 
-typedef HashJoinTableData *HashJoinTable;
-
 #endif   /* HASHJOIN_H */

src/include/executor/nodeHash.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/executor/nodeHash.h,v 1.35 2004/12/31 22:03:29 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/executor/nodeHash.h,v 1.36 2005/03/06 22:15:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -25,18 +25,20 @@ extern void ExecReScanHash(HashState *node, ExprContext *exprCtxt);
 extern HashJoinTable ExecHashTableCreate(Hash *node, List *hashOperators);
 extern void ExecHashTableDestroy(HashJoinTable hashtable);
 extern void ExecHashTableInsert(HashJoinTable hashtable,
-					ExprContext *econtext,
-					List *hashkeys);
-extern int ExecHashGetBucket(HashJoinTable hashtable,
-				  ExprContext *econtext,
-				  List *hashkeys);
-extern int	ExecHashGetBatch(int bucketno, HashJoinTable hashtable);
-extern HeapTuple ExecScanHashBucket(HashJoinState *hjstate, List *hjclauses,
-				   ExprContext *econtext);
-extern void ExecHashTableReset(HashJoinTable hashtable, long ntuples);
+								HeapTuple tuple,
+								uint32 hashvalue);
+extern uint32 ExecHashGetHashValue(HashJoinTable hashtable,
+								   ExprContext *econtext,
+								   List *hashkeys);
+extern void ExecHashGetBucketAndBatch(HashJoinTable hashtable,
+									  uint32 hashvalue,
+									  int *bucketno,
+									  int *batchno);
+extern HeapTuple ExecScanHashBucket(HashJoinState *hjstate,
+									ExprContext *econtext);
+extern void ExecHashTableReset(HashJoinTable hashtable);
 extern void ExecChooseHashTableSize(double ntuples, int tupwidth,
-						int *virtualbuckets,
-						int *physicalbuckets,
+						int *numbuckets,
 						int *numbatches);
 
 #endif   /* NODEHASH_H */

src/include/executor/nodeHashjoin.h

@@ -1,13 +1,13 @@
 /*-------------------------------------------------------------------------
  *
  * nodeHashjoin.h
- *
+ *	  prototypes for nodeHashjoin.c
  *
  *
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/executor/nodeHashjoin.h,v 1.28 2004/12/31 22:03:29 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/executor/nodeHashjoin.h,v 1.29 2005/03/06 22:15:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -15,6 +15,7 @@
 #define NODEHASHJOIN_H
 
 #include "nodes/execnodes.h"
+#include "storage/buffile.h"
 
 extern int	ExecCountSlotsHashJoin(HashJoin *node);
 extern HashJoinState *ExecInitHashJoin(HashJoin *node, EState *estate);
@@ -22,6 +23,7 @@ extern TupleTableSlot *ExecHashJoin(HashJoinState *node);
 extern void ExecEndHashJoin(HashJoinState *node);
 extern void ExecReScanHashJoin(HashJoinState *node, ExprContext *exprCtxt);
 
-extern void ExecHashJoinSaveTuple(HeapTuple heapTuple, BufFile *file);
+extern void ExecHashJoinSaveTuple(HeapTuple heapTuple, uint32 hashvalue,
+								  BufFile **fileptr);
 
 #endif   /* NODEHASHJOIN_H */

src/include/nodes/execnodes.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.122 2004/12/31 22:03:34 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.123 2005/03/06 22:15:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -15,7 +15,6 @@
 #define EXECNODES_H
 
 #include "access/relscan.h"
-#include "executor/hashjoin.h"
 #include "executor/tuptable.h"
 #include "fmgr.h"
 #include "nodes/bitmapset.h"
@@ -985,11 +984,13 @@ typedef struct MergeJoinState
  *	 HashJoinState information
  *
  *		hj_HashTable			hash table for the hashjoin
+ *								(NULL if table not built yet)
+ *		hj_CurHashValue			hash value for current outer tuple
  *		hj_CurBucketNo			bucket# for current outer tuple
  *		hj_CurTuple				last inner tuple matched to current outer
  *								tuple, or NULL if starting search
- *								(CurBucketNo and CurTuple are meaningless
- *								 unless OuterTupleSlot is nonempty!)
+ *								(CurHashValue, CurBucketNo and CurTuple are
+ *								 undefined if OuterTupleSlot is empty!)
  *		hj_OuterHashKeys		the outer hash keys in the hashjoin condition
  *		hj_InnerHashKeys		the inner hash keys in the hashjoin condition
  *		hj_HashOperators		the join operators in the hashjoin condition
@@ -998,14 +999,19 @@ typedef struct MergeJoinState
  *		hj_NullInnerTupleSlot	prepared null tuple for left outer joins
  *		hj_NeedNewOuter			true if need new outer tuple on next call
  *		hj_MatchedOuter			true if found a join match for current outer
- *		hj_hashdone				true if hash-table-build phase is done
  * ----------------
  */
+
+/* these structs are defined in executor/hashjoin.h: */
+typedef struct HashJoinTupleData *HashJoinTuple;
+typedef struct HashJoinTableData *HashJoinTable;
+
 typedef struct HashJoinState
 {
 	JoinState	js;				/* its first field is NodeTag */
 	List	   *hashclauses;	/* list of ExprState nodes */
 	HashJoinTable hj_HashTable;
+	uint32		hj_CurHashValue;
 	int			hj_CurBucketNo;
 	HashJoinTuple hj_CurTuple;
 	List	   *hj_OuterHashKeys;		/* list of ExprState nodes */
@@ -1016,7 +1022,6 @@ typedef struct HashJoinState
 	TupleTableSlot *hj_NullInnerTupleSlot;
 	bool		hj_NeedNewOuter;
 	bool		hj_MatchedOuter;
-	bool		hj_hashdone;
 } HashJoinState;
 
 

src/include/utils/selfuncs.h

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/selfuncs.h,v 1.21 2004/12/31 22:03:46 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/utils/selfuncs.h,v 1.22 2005/03/06 22:15:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -121,7 +121,7 @@ extern double estimate_num_groups(Query *root, List *groupExprs,
 					double input_rows);
 
 extern Selectivity estimate_hash_bucketsize(Query *root, Node *hashkey,
-						 int nbuckets);
+						 double nbuckets);
 
 extern Datum btcostestimate(PG_FUNCTION_ARGS);
 extern Datum rtcostestimate(PG_FUNCTION_ARGS);