Remove ruleutils.c's use of varnoold/varoattno as a shortcut for determining

what a Var node refers to.  This is no longer necessary because the new
flat-range-table representation of plan trees makes it relatively easy to dig
down through child plan levels to find the original reference; and to keep
doing it that way, we'd have to store joinaliasvars lists in flattened RTEs,
as demonstrated by bug report from Leszek Trenkner.  This change makes
varnoold/varoattno truly just debug aids, which wasn't quite the case before.
Perhaps we should drop them, or only have them in assert-enabled builds?

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 46cf1dd45af6374aadcde36bd12a4fcc34430556..d5de627df1b15bafaf6df191d2814043bc006a25 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 1.257 2007/03/27 23:21:10 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.258 2007/05/24 18:58:42 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2598,20 +2598,14 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
 
        /*
         * Try to find the relevant RTE in this rtable.  In a plan tree, it's
-        * likely that varno is OUTER or INNER, in which case we try to use
-        * varnoold instead.  If the Var references an expression computed by a
-        * subplan, varnoold will be 0, and we must dig down into the subplans.
+        * likely that varno is OUTER or INNER, in which case we must dig down
+        * into the subplans.
         */
        if (var->varno >= 1 && var->varno <= list_length(dpns->rtable))
        {
                rte = rt_fetch(var->varno, dpns->rtable);
                attnum = var->varattno;
        }
-       else if (var->varnoold >= 1 && var->varnoold <= list_length(dpns->rtable))
-       {
-               rte = rt_fetch(var->varnoold, dpns->rtable);
-               attnum = var->varoattno;
-       }
        else if (var->varno == OUTER && dpns->outer_plan)
        {
                TargetEntry *tle;
@@ -2631,9 +2625,11 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
                 * Force parentheses because our caller probably assumed a Var is a
                 * simple expression.
                 */
-               appendStringInfoChar(buf, '(');
+               if (!IsA(tle->expr, Var))
+                       appendStringInfoChar(buf, '(');
                get_rule_expr((Node *) tle->expr, context, true);
-               appendStringInfoChar(buf, ')');
+               if (!IsA(tle->expr, Var))
+                       appendStringInfoChar(buf, ')');
 
                dpns->outer_plan = save_outer;
                dpns->inner_plan = save_inner;
@@ -2658,9 +2654,11 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
                 * Force parentheses because our caller probably assumed a Var is a
                 * simple expression.
                 */
-               appendStringInfoChar(buf, '(');
+               if (!IsA(tle->expr, Var))
+                       appendStringInfoChar(buf, '(');
                get_rule_expr((Node *) tle->expr, context, true);
-               appendStringInfoChar(buf, ')');
+               if (!IsA(tle->expr, Var))
+                       appendStringInfoChar(buf, ')');
 
                dpns->outer_plan = save_outer;
                dpns->inner_plan = save_inner;
@@ -2700,7 +2698,13 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
                         * simple reference, we have to just print the unqualified
                         * variable name (this can only happen with columns that were
                         * merged by USING or NATURAL clauses).
+                        *
+                        * This wouldn't work in decompiling plan trees, because we don't
+                        * store joinaliasvars lists after planning; but a plan tree
+                        * should never contain a join alias variable.
                         */
+                       if (rte->joinaliasvars == NIL)
+                               elog(ERROR, "cannot decompile join alias var in plan tree");
                        if (attnum > 0)
                        {
                                Var                *aliasvar;
@@ -2798,9 +2802,7 @@ get_name_for_var_field(Var *var, int fieldno,
        /*
         * Try to find the relevant RTE in this rtable.  In a plan tree, it's
         * likely that varno is OUTER or INNER, in which case we must dig down
-        * into the subplans.  (We can't shortcut with varnoold here, because
-        * it might reference a SUBQUERY RTE; we have to dig down to the
-        * SubqueryScan plan level to cope with that.  See below.)
+        * into the subplans.
         */
        if (var->varno >= 1 && var->varno <= list_length(dpns->rtable))
        {
@@ -2963,6 +2965,8 @@ get_name_for_var_field(Var *var, int fieldno,
                        break;
                case RTE_JOIN:
                        /* Join RTE --- recursively inspect the alias variable */
+                       if (rte->joinaliasvars == NIL)
+                               elog(ERROR, "cannot decompile join alias var in plan tree");
                        Assert(attnum > 0 && attnum <= list_length(rte->joinaliasvars));
                        expr = (Node *) list_nth(rte->joinaliasvars, attnum - 1);
                        if (IsA(expr, Var))