Defend against JOINs having more than 32K columns altogether. We cannot

currently support this because we must be able to build Vars referencing
join columns, and varattno is only 16 bits wide.  Perhaps this should be
improved in future, but considering that it never came up before, I'm not
sure the problem is worth much effort.  Per bug #4070 from Marcello
Ceschia.

The problem seems largely academic in 8.0 and 7.4, because they have
(different) O(N^2) performance issues with such wide joins, but
back-patch all the way anyway.

diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index 180ba985129e0268ec38f0ca14540664f364db4f..bc5c54d28012c6e744d105e831c0e1aef6130ad3 100644 (file)
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/parser/parse_relation.c,v 1.90.2.2 2005/05/29 17:10:52 tgl Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/parser/parse_relation.c,v 1.90.2.3 2008/04/05 01:59:01 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1072,6 +1072,16 @@ addRangeTableEntryForJoin(ParseState *pstate,
        Alias      *eref;
        int                     numaliases;
 
+       /*
+        * Fail if join has too many columns --- we must be able to reference
+        * any of the columns with an AttrNumber.
+        */
+       if (length(aliasvars) > MaxAttrNumber)
+               ereport(ERROR,
+                               (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+                                errmsg("joins can have at most %d columns",
+                                               MaxAttrNumber)));
+
        rte->rtekind = RTE_JOIN;
        rte->relid = InvalidOid;
        rte->subquery = NULL;

diff --git a/src/include/access/attnum.h b/src/include/access/attnum.h
index 16d16f5a9df381d168447a655790e96361830090..25f0d4ee3682b6b2879c3036a15769d6fa1e70c3 100644 (file)
--- a/src/include/access/attnum.h
+++ b/src/include/access/attnum.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: attnum.h,v 1.17 2003/08/04 02:40:10 momjian Exp $
+ * $Id: attnum.h,v 1.17.4.1 2008/04/05 01:59:01 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,6 +21,7 @@
 typedef int16 AttrNumber;
 
 #define InvalidAttrNumber              0
+#define MaxAttrNumber                  32767
 
 /* ----------------
  *             support macros