Make atmsort recognize an ORDER BY in an OVER or WITHIN GROUP construct.

This silences false regression failures caused by row order differences in
some queries that use those constructs. While we don't have such false
failures in the regression suite right now, the upcoming rewrite of the
window functions implementation will change the plans for some queries, and
would cause some.

src/test/regress/atmsort.pm

@@ -1429,20 +1429,44 @@ sub atmsort_bigloop
 
                 print $atmsort_outfh $apref, $ini;
 
+                # If there is an ORDER BY in the query, then the results must
+                # be in the order that we have memorized in the expected
+                # output. Otherwise, the order of the rows is not
+                # well-defined, so we sort them before comparing, to mask out
+                # any differences in the order.
+                #
+                # This isn't foolproof, and will get fooled by ORDER BYs in
+                # subqueries, for example. But it catches the commmon cases.
                 if (defined($sql_statement)
                     && length($sql_statement)
                     && !defined($directive->{order_none})
                     # multiline match
                     && ($sql_statement =~ m/select.*order.*by/is))
                 {
-                    $has_order = 1; # so do *not* sort output
-                    $directive->{sql_statement} = $sql_statement;
+                    # There was an ORDER BY. But if it was part of an
+                    # "agg() OVER (ORDER BY ...)" or "WITHIN GROUP (ORDER BY
+                    # ...)" construct, ignore it, because those constructs
+                    # don't mean that the final result has to be in order.
+                    my $t = $sql_statement;
+                    $t =~ s/over\s*\(order\s+by.*\)/xx/isg;
+                    $t =~ s/over\s*\((partition\s+by.*)?order\s+by.*\)/xx/isg;
+                    $t =~ s/window\s+\w+\s+as\s+\((partition\s+by.*)?order\s+by.*\)/xx/isg;
+                    $t =~ s/within\s+group\s*\((order\s+by.*)\)/xx/isg;
+
+                    if ($t =~ m/order\s+by/is)
+                    {
+                        $has_order = 1; # so do *not* sort output
+                    }
+                    else
+                    {
+                        $has_order = 0; # need to sort query output
+                    }
                 }
                 else
                 {
                     $has_order = 0; # need to sort query output
-                    $directive->{sql_statement} = $sql_statement;
                 }
+                $directive->{sql_statement} = $sql_statement;
                 $sql_statement = '';
 
                 $getrows = 1;