Fix performance issue in exprTypmod(): for a COALESCE expression, it

recursed twice on its first argument, leading to exponential time spent
on a deep nest of COALESCEs ... such as a deeply nested FULL JOIN would
produce.  Per report from Matt Carter.

diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index 6c0c53d0748b9b4ad24314de15e9fc3d0fff889d..2cfa43caf9afaa9985ea574bd1dffbb2f9ef7f20 100644 (file)
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.163.2.3 2005/05/25 02:13:48 ishii Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.163.2.4 2005/11/18 23:08:43 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1425,8 +1425,12 @@ exprTypmod(Node *expr)
                                int32           typmod;
                                List       *arg;
 
+                               if (exprType((Node *) lfirst(cexpr->args)) != coalescetype)
+                                       return -1;
                                typmod = exprTypmod((Node *) lfirst(cexpr->args));
-                               foreach(arg, cexpr->args)
+                               if (typmod < 0)
+                                       return -1;      /* no point in trying harder */
+                               foreach(arg, lnext(cexpr->args))
                                {
                                        Node       *e = (Node *) lfirst(arg);