From f796387b602c8d0c538eba6b96bf86c399c4cd36 Mon Sep 17 00:00:00 2001 From: "Marc G. Fournier" Date: Mon, 19 Aug 1996 01:52:36 +0000 Subject: [PATCH] |From: Dan McGuirk | |This patch fixes a backend crash that happens sometimes when you try to |join on a field that contains NULL in some rows. Postgres tries to |compute a hash value of the field you're joining on, but when the field |is NULL, the pointer it thinks is pointing to the data is really just |pointing to random memory. This forces the hash value of NULL to be 0. | |It seems that nothing matches NULL on joins, even other NULL's (with or |without this patch). Is that what's supposed to happen? | --- src/backend/executor/nodeHash.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/src/backend/executor/nodeHash.c b/src/backend/executor/nodeHash.c index 9ea00ed237..6a476bac59 100644 --- a/src/backend/executor/nodeHash.c +++ b/src/backend/executor/nodeHash.c @@ -7,7 +7,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/executor/nodeHash.c,v 1.3 1996/07/26 20:03:21 scrappy Exp $ + * $Header: /cvsroot/pgsql/src/backend/executor/nodeHash.c,v 1.4 1996/08/19 01:52:36 scrappy Exp $ * *------------------------------------------------------------------------- */ @@ -527,6 +527,16 @@ ExecHashGetBucket(HashJoinTable hashtable, */ keyval = ExecEvalVar(hashkey, econtext, &isNull); + /* + * keyval could be null, so we better point it to something + * valid before trying to run hashFunc on it. --djm 8/17/96 + */ + if(isNull) { + execConstByVal = 0; + execConstLen = 0; + keyval = (Datum)""; + } + /* ------------------ * compute the hash function * ------------------