diff --git a/src/backend/access/hash/hashfunc.c b/src/backend/access/hash/hashfunc.c
index d9b5524b0a..39a58c0899 100644
--- a/src/backend/access/hash/hashfunc.c
+++ b/src/backend/access/hash/hashfunc.c
@@ -1,19 +1,26 @@
 /*-------------------------------------------------------------------------
  *
  * hashfunc.c
- *	  Comparison functions for hash access method.
+ *	  Support functions for hash access method.
  *
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/hash/hashfunc.c,v 1.51 2007/04/02 03:49:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/hash/hashfunc.c,v 1.52 2007/06/01 15:33:18 tgl Exp $
  *
  * NOTES
  *	  These functions are stored in pg_amproc.	For each operator class
- *	  defined on hash tables, they compute the hash value of the argument.
+ *	  defined for hash indexes, they compute the hash value of the argument.
  *
+ *	  Additional hash functions appear in /utils/adt/ files for various
+ *	  specialized datatypes.
+ *
+ *	  It is expected that every bit of a hash function's 32-bit result is
+ *	  as random as every other; failure to ensure this is likely to lead
+ *	  to poor performance of hash joins, for example.  In most cases a hash
+ *	  function should use hash_any() or its variant hash_uint32().
  *-------------------------------------------------------------------------
  */
 
@@ -26,19 +33,19 @@
 Datum
 hashchar(PG_FUNCTION_ARGS)
 {
-	PG_RETURN_UINT32(~((uint32) PG_GETARG_CHAR(0)));
+	return hash_uint32((int32) PG_GETARG_CHAR(0));
 }
 
 Datum
 hashint2(PG_FUNCTION_ARGS)
 {
-	PG_RETURN_UINT32(~((uint32) PG_GETARG_INT16(0)));
+	return hash_uint32((int32) PG_GETARG_INT16(0));
 }
 
 Datum
 hashint4(PG_FUNCTION_ARGS)
 {
-	PG_RETURN_UINT32(~PG_GETARG_UINT32(0));
+	return hash_uint32(PG_GETARG_INT32(0));
 }
 
 Datum
@@ -59,23 +66,23 @@ hashint8(PG_FUNCTION_ARGS)
 
 	lohalf ^= (val >= 0) ? hihalf : ~hihalf;
 
-	PG_RETURN_UINT32(~lohalf);
+	return hash_uint32(lohalf);
 #else
 	/* here if we can't count on "x >> 32" to work sanely */
-	PG_RETURN_UINT32(~((uint32) PG_GETARG_INT64(0)));
+	return hash_uint32((int32) PG_GETARG_INT64(0));
 #endif
 }
 
 Datum
 hashoid(PG_FUNCTION_ARGS)
 {
-	PG_RETURN_UINT32(~((uint32) PG_GETARG_OID(0)));
+	return hash_uint32((uint32) PG_GETARG_OID(0));
 }
 
 Datum
 hashenum(PG_FUNCTION_ARGS)
 {
-    PG_RETURN_UINT32(~((uint32) PG_GETARG_OID(0)));
+	return hash_uint32((uint32) PG_GETARG_OID(0));
 }
 
 Datum
@@ -283,6 +290,31 @@ hash_any(register const unsigned char *k, register int keylen)
 			/* case 0: nothing left to add */
 	}
 	mix(a, b, c);
+
+	/* report the result */
+	return UInt32GetDatum(c);
+}
+
+/*
+ * hash_uint32() -- hash a 32-bit value
+ *
+ * This has the same result (at least on little-endian machines) as
+ *		hash_any(&k, sizeof(uint32))
+ * but is faster and doesn't force the caller to store k into memory.
+ */
+Datum
+hash_uint32(uint32 k)
+{
+	register uint32 a,
+				b,
+				c;
+
+	a = 0x9e3779b9 + k;
+	b = 0x9e3779b9;
+	c = 3923095 + (uint32) sizeof(uint32);
+
+	mix(a, b, c);
+
 	/* report the result */
 	return UInt32GetDatum(c);
 }
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index 86a9fb332c..bc77363fbf 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -14,13 +14,14 @@
  * Copyright (c) 2003-2007, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/bitmapset.c,v 1.12 2007/01/05 22:19:29 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/bitmapset.c,v 1.13 2007/06/01 15:33:18 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
 
 #include "nodes/bitmapset.h"
+#include "access/hash.h"
 
 
 #define WORDNUM(x)	((x) / BITS_PER_BITMAPWORD)
@@ -769,36 +770,23 @@ bms_first_member(Bitmapset *a)
  *
  * Note: we must ensure that any two bitmapsets that are bms_equal() will
  * hash to the same value; in practice this means that trailing all-zero
- * words cannot affect the result.	The circular-shift-and-XOR hash method
- * used here has this property, so long as we work from back to front.
- *
- * Note: you might wonder why we bother with the circular shift; at first
- * glance a straight longitudinal XOR seems as good and much simpler.  The
- * reason is empirical: this gives a better distribution of hash values on
- * the bitmapsets actually generated by the planner.  A common way to have
- * multiword bitmapsets is "a JOIN b JOIN c JOIN d ...", which gives rise
- * to rangetables in which base tables and JOIN nodes alternate; so
- * bitmapsets of base table RT indexes tend to use only odd-numbered or only
- * even-numbered bits.	A straight longitudinal XOR would preserve this
- * property, leading to a much smaller set of possible outputs than if
- * we include a shift.
+ * words must not affect the result.  Hence we strip those before applying
+ * hash_any().
  */
 uint32
 bms_hash_value(const Bitmapset *a)
 {
-	bitmapword	result = 0;
-	int			wordnum;
+	int			lastword;
 
-	if (a == NULL || a->nwords <= 0)
+	if (a == NULL)
 		return 0;				/* All empty sets hash to 0 */
-	for (wordnum = a->nwords; --wordnum > 0;)
+	for (lastword = a->nwords; --lastword >= 0;)
 	{
-		result ^= a->words[wordnum];
-		if (result & ((bitmapword) 1 << (BITS_PER_BITMAPWORD - 1)))
-			result = (result << 1) | 1;
-		else
-			result = (result << 1);
+		if (a->words[lastword] != 0)
+			break;
 	}
-	result ^= a->words[0];
-	return (uint32) result;
+	if (lastword < 0)
+		return 0;				/* All empty sets hash to 0 */
+	return DatumGetUInt32(hash_any((const unsigned char *) a->words,
+								   (lastword + 1) * sizeof(bitmapword)));
 }
diff --git a/src/backend/utils/hash/hashfn.c b/src/backend/utils/hash/hashfn.c
index 6eeedc9383..e1e65c0350 100644
--- a/src/backend/utils/hash/hashfn.c
+++ b/src/backend/utils/hash/hashfn.c
@@ -9,7 +9,13 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/hash/hashfn.c,v 1.30 2007/01/05 22:19:43 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/hash/hashfn.c,v 1.31 2007/06/01 15:33:18 tgl Exp $
+ *
+ * NOTES
+ *	  It is expected that every bit of a hash function's 32-bit result is
+ *	  as random as every other; failure to ensure this is likely to lead
+ *	  to poor performance of hash tables.  In most cases a hash
+ *	  function should use hash_any() or its variant hash_uint32().
  *
  *-------------------------------------------------------------------------
  */
@@ -58,8 +64,7 @@ uint32
 oid_hash(const void *key, Size keysize)
 {
 	Assert(keysize == sizeof(Oid));
-	/* We don't actually bother to do anything to the OID value ... */
-	return (uint32) *((const Oid *) key);
+	return DatumGetUInt32(hash_uint32((uint32) *((const Oid *) key)));
 }
 
 /*
diff --git a/src/include/access/hash.h b/src/include/access/hash.h
index 2bd314a8aa..e7f59e2da8 100644
--- a/src/include/access/hash.h
+++ b/src/include/access/hash.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/hash.h,v 1.81 2007/05/30 20:12:02 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/access/hash.h,v 1.82 2007/06/01 15:33:18 tgl Exp $
  *
  * NOTES
  *		modeled after Margo Seltzer's hash implementation for unix.
@@ -265,6 +265,7 @@ extern Datum hashname(PG_FUNCTION_ARGS);
 extern Datum hashtext(PG_FUNCTION_ARGS);
 extern Datum hashvarlena(PG_FUNCTION_ARGS);
 extern Datum hash_any(register const unsigned char *k, register int keylen);
+extern Datum hash_uint32(uint32 k);
 
 /* private routines */
 
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 9ae142387c..b71f718776 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -37,7 +37,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.407 2007/05/21 17:10:29 petere Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.408 2007/06/01 15:33:19 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	200705211
+#define CATALOG_VERSION_NO	200706011
 
 #endif