Fix pg_get_ruledef() so that negative numeric constants are parenthesized.

This is needed because :: casting binds more tightly than minus, so for
example -1::integer is not the same as (-1)::integer, and there are cases
where the difference is important.  In particular this caused a failure
in SELECT DISTINCT ... ORDER BY ... where expressions that should have
matched were seen as different by the parser; but I suspect that there
could be other cases where failure to parenthesize leads to subtler
semantic differences in reloaded rules.  Per report from Alexandr Popov.

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 8578b5c7cb54ca0633f3d76b47d08a2eb6289fb4..c2410efbba0d4ba81d1a2ffb9bc52bfcc515ef9d 100644 (file)
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.269.2.1 2008/05/03 23:19:27 tgl Exp $
+ *   $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.269.2.2 2008/06/06 17:59:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -4472,10 +4472,19 @@ get_const_expr(Const *constval, deparse_context *context, int showtype)
                 *
                 * In reality we only need to defend against infinity and NaN,
                 * so we need not get too crazy about pattern matching here.
+                *
+                * There is a special-case gotcha: if the constant is signed,
+                * we need to parenthesize it, else the parser might see a
+                * leading plus/minus as binding less tightly than adjacent
+                * operators --- particularly, the cast that we might attach
+                * below.
                 */
                if (strspn(extval, "0123456789+-eE.") == strlen(extval))
                {
-                   appendStringInfoString(buf, extval);
+                   if (extval[0] == '+' || extval[0] == '-')
+                       appendStringInfo(buf, "(%s)", extval);
+                   else
+                       appendStringInfoString(buf, extval);
                    if (strcspn(extval, "eE.") != strlen(extval))
                        isfloat = true; /* it looks like a float */
                }