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 6d5fb1894061d79ba76ff51936f2be98840ff6ad..68855a700741ff47e33832779f4e9065250969e6 100644 (file)
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/parser/parse_relation.c,v 1.130 2008/01/01 19:45:51 momjian Exp $
+ *       $PostgreSQL: pgsql/src/backend/parser/parse_relation.c,v 1.131 2008/04/05 01:58:20 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1025,6 +1025,16 @@ 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 (list_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 c1ec4947ffe6eec4d0bbbf5f94c407fc4e7c0ea4..033f2ee786d81580f726dc01c92d16f8e8f94533 100644 (file)
--- a/src/include/access/attnum.h
+++ b/src/include/access/attnum.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/attnum.h,v 1.24 2008/01/01 19:45:56 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/access/attnum.h,v 1.25 2008/04/05 01:58:20 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,6 +21,7 @@
 typedef int16 AttrNumber;
 
 #define InvalidAttrNumber              0
+#define MaxAttrNumber                  32767
 
 /* ----------------
  *             support macros