From 974bdd94f99a715dacc0c1c00b4aff89342e79a7 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 21 Jun 1999 01:18:02 +0000
Subject: [PATCH] On second thought, expression_tree_walker should handle bare
SubLink nodes after all ...
---
src/backend/optimizer/util/clauses.c | 20 +++++++++++-----
src/backend/parser/parse_agg.c | 36 ++++++++--------------------
2 files changed, 24 insertions(+), 32 deletions(-)
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 3427302c8de..ad320dcd047 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.36 1999/06/19 03:41:45 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.37 1999/06/21 01:18:02 tgl Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
@@ -810,7 +810,8 @@ CommuteClause(Node *clause)
* The walker routine should return "false" to continue the tree walk, or
* "true" to abort the walk and immediately return "true" to the top-level
* caller. This can be used to short-circuit the traversal if the walker
- * has found what it came for.
+ * has found what it came for. "false" is returned to the top-level caller
+ * iff no invocation of the walker returned "true".
*
* The node types handled by expression_tree_walker include all those
* normally found in target lists and qualifier clauses during the planning
@@ -827,10 +828,11 @@ CommuteClause(Node *clause)
* appropriate behavior by recognizing subplan nodes and doing the right
* thing.
*
- * Bare SubLink nodes (without a SUBPLAN_EXPR) will trigger an error unless
- * detected and processed by the walker. We expect that walkers used before
- * sublink processing is done will handle them properly. (XXX Maybe ignoring
- * them would be better default behavior?)
+ * Bare SubLink nodes (without a SUBPLAN_EXPR) are handled by recursing into
+ * the "lefthand" argument list only. (A bare SubLink should be seen only if
+ * the tree has not yet been processed by subselect.c.) Again, this can be
+ * overridden by the walker, but it seems to be the most useful default
+ * behavior.
*--------------------
*/
@@ -923,6 +925,12 @@ expression_tree_walker(Node *node, bool (*walker) (), void *context)
return true;
}
break;
+ case T_SubLink:
+ /* A "bare" SubLink (note we will not come here if we found
+ * a SUBPLAN_EXPR node above). Examine the lefthand side,
+ * but not the oper list nor the subquery.
+ */
+ return walker(((SubLink *) node)->lefthand, context);
case T_List:
foreach(temp, (List *) node)
{
diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c
index f7374171b20..80662278f70 100644
--- a/src/backend/parser/parse_agg.c
+++ b/src/backend/parser/parse_agg.c
@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/parser/parse_agg.c,v 1.22 1999/06/19 03:48:31 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/parser/parse_agg.c,v 1.23 1999/06/21 01:18:02 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -43,9 +43,7 @@ static bool exprIsAggOrGroupCol_walker(Node *node, List *groupClauses);
* Returns true if any aggregate found.
*
* NOTE: we assume that the given clause has been transformed suitably for
- * parser output. This means we can use the planner's expression_tree_walker,
- * except that we have to process SubLink nodes specially, since they haven't
- * been turned into SubPlan nodes yet.
+ * parser output. This means we can use the planner's expression_tree_walker.
*/
static bool
contain_agg_clause(Node *clause)
@@ -60,12 +58,6 @@ contain_agg_clause_walker(Node *node, void *context)
return false;
if (IsA(node, Aggref))
return true; /* abort the tree traversal and return true */
- if (IsA(node, SubLink))
- {
- /* Examine the lefthand side, but not the oper list nor the subquery */
- SubLink *sublink = (SubLink *) node;
- return contain_agg_clause_walker((Node *) sublink->lefthand, context);
- }
return expression_tree_walker(node, contain_agg_clause_walker, context);
}
@@ -75,16 +67,15 @@ contain_agg_clause_walker(Node *node, void *context)
* other than within the arguments of aggregate functions.
*
* NOTE: we assume that the given clause has been transformed suitably for
- * parser output. This means we can use the planner's expression_tree_walker,
- * except that we have to process SubLink nodes specially, since they haven't
- * been turned into SubPlan nodes yet.
+ * parser output. This means we can use the planner's expression_tree_walker.
*
- * NOTE: in the case of a SubLink, we do not descend into the subquery. This
- * means we will fail to detect ungrouped columns that appear as outer-level
- * variables within a subquery. That seems unreasonably hard to handle here.
- * Instead, we expect the planner to check for ungrouped columns after it's
- * found all the outer-level references inside the subquery and converted
- * them into a list of parameters for the subquery.
+ * NOTE: in the case of a SubLink, expression_tree_walker does not descend
+ * into the subquery. This means we will fail to detect ungrouped columns
+ * that appear as outer-level variables within a subquery. That case seems
+ * unreasonably hard to handle here. Instead, we expect the planner to check
+ * for ungrouped columns after it's found all the outer-level references
+ * inside the subquery and converted them into a list of parameters for the
+ * subquery.
*/
static bool
exprIsAggOrGroupCol(Node *expr, List *groupClauses)
@@ -128,13 +119,6 @@ exprIsAggOrGroupCol_walker(Node *node, List *groupClauses)
return false; /* outer-level Var is acceptable */
}
/* Otherwise, recurse. */
- if (IsA(node, SubLink))
- {
- /* Examine the lefthand side, but not the oper list nor the subquery */
- SubLink *sublink = (SubLink *) node;
- return exprIsAggOrGroupCol_walker((Node *) sublink->lefthand,
- groupClauses);
- }
return expression_tree_walker(node, exprIsAggOrGroupCol_walker,
(void *) groupClauses);
}
--
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