Revise hash join and hash aggregation code to use the same datatype-

specific hash functions used by hash indexes, rather than the old
not-datatype-aware ComputeHashFunc routine.  This makes it safe to do
hash joining on several datatypes that previously couldn't use hashing.
The sets of datatypes that are hash indexable and hash joinable are now
exactly the same, whereas before each had some that weren't in the other.

1 files changed, 38 insertions, 6 deletions

diff --git a/src/backend/access/hash/hashfunc.c b/src/backend/access/hash/hashfunc.c
index e6595de072..a82b8b32d5 100644
--- a/src/backend/access/hash/hashfunc.c
+++ b/src/backend/access/hash/hashfunc.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/hash/hashfunc.c,v 1.35 2002/09/04 20:31:09 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/hash/hashfunc.c,v 1.36 2003/06/22 22:04:54 tgl Exp $
  *
  * NOTES
  *	  These functions are stored in pg_amproc.	For each operator class
@@ -22,6 +22,7 @@
 #include "access/hash.h"
 
 
+/* Note: this is used for both "char" and boolean datatypes */
 Datum
 hashchar(PG_FUNCTION_ARGS)
 {
@@ -58,6 +59,14 @@ hashfloat4(PG_FUNCTION_ARGS)
 {
 	float4		key = PG_GETARG_FLOAT4(0);
 
+	/*
+	 * On IEEE-float machines, minus zero and zero have different bit patterns
+	 * but should compare as equal.  We must ensure that they have the same
+	 * hash value, which is most easily done this way:
+	 */
+	if (key == (float4) 0)
+		PG_RETURN_UINT32(0);
+
 	return hash_any((unsigned char *) &key, sizeof(key));
 }
 
@@ -66,6 +75,14 @@ hashfloat8(PG_FUNCTION_ARGS)
 {
 	float8		key = PG_GETARG_FLOAT8(0);
 
+	/*
+	 * On IEEE-float machines, minus zero and zero have different bit patterns
+	 * but should compare as equal.  We must ensure that they have the same
+	 * hash value, which is most easily done this way:
+	 */
+	if (key == (float8) 0)
+		PG_RETURN_UINT32(0);
+
 	return hash_any((unsigned char *) &key, sizeof(key));
 }
 
@@ -77,11 +94,6 @@ hashoidvector(PG_FUNCTION_ARGS)
 	return hash_any((unsigned char *) key, INDEX_MAX_KEYS * sizeof(Oid));
 }
 
-/*
- * Note: hashint2vector currently can't be used as a user hash table
- * hash function, because it has no pg_proc entry.	We only need it
- * for catcache indexing.
- */
 Datum
 hashint2vector(PG_FUNCTION_ARGS)
 {
@@ -102,6 +114,26 @@ hashname(PG_FUNCTION_ARGS)
 	return hash_any((unsigned char *) key, keylen);
 }
 
+Datum
+hashtext(PG_FUNCTION_ARGS)
+{
+	text	   *key = PG_GETARG_TEXT_P(0);
+	Datum		result;
+
+	/*
+	 * Note: this is currently identical in behavior to hashvarlena,
+	 * but it seems likely that we may need to do something different
+	 * in non-C locales.  (See also hashbpchar, if so.)
+	 */
+	result = hash_any((unsigned char *) VARDATA(key),
+					  VARSIZE(key) - VARHDRSZ);
+
+	/* Avoid leaking memory for toasted inputs */
+	PG_FREE_IF_COPY(key, 0);
+
+	return result;
+}
+
 /*
  * hashvarlena() can be used for any varlena datatype in which there are
  * no non-significant bits, ie, distinct bitpatterns never compare as equal.