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 c93aa1d7b07710407c79b24228471a370d9834a1..65c2c7394e7ecf1e6cf968e27cd6c8bc6b54a17e 100644 (file)
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -4042,10 +4042,19 @@ 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 */
                                }