From d4d32eefdf3df4eb9aadea08e3d07af753457fbb Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 8 Jul 2010 00:14:04 +0000
Subject: [PATCH] Fix "cannot handle unplanned sub-select" error that can occur
when a sub-select contains a join alias reference that expands into an
expression containing another sub-select. Per yesterday's report from Merlin
Moncure and subsequent off-list investigation.
Back-patch to 7.4. Older versions didn't attempt to flatten sub-selects in
ways that would trigger this problem.
---
src/backend/optimizer/util/var.c | 31 +++++++++++++++++++++++--
src/test/regress/expected/subselect.out | 14 +++++++++++
src/test/regress/sql/subselect.sql | 12 ++++++++++
3 files changed, 55 insertions(+), 2 deletions(-)
diff --git a/src/backend/optimizer/util/var.c b/src/backend/optimizer/util/var.c
index 402c9eaffbb..fdd12392748 100644
--- a/src/backend/optimizer/util/var.c
+++ b/src/backend/optimizer/util/var.c
@@ -14,7 +14,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/util/var.c,v 1.87 2010/01/02 16:57:48 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/util/var.c,v 1.88 2010/07/08 00:14:03 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -63,6 +63,8 @@ typedef struct
{
PlannerInfo *root;
int sublevels_up;
+ bool possible_sublink; /* could aliases include a SubLink? */
+ bool inserted_sublink; /* have we inserted a SubLink? */
} flatten_join_alias_vars_context;
static bool pull_varnos_walker(Node *node,
@@ -688,6 +690,14 @@ pull_var_clause_walker(Node *node, pull_var_clause_context *context)
* This also adjusts relid sets found in some expression node types to
* substitute the contained base rels for any join relid.
*
+ * If a JOIN contains sub-selects that have been flattened, its join alias
+ * entries might now be arbitrary expressions, not just Vars. This affects
+ * this function in one important way: we might find ourselves inserting
+ * SubLink expressions into subqueries, and we must make sure that their
+ * Query.hasSubLinks fields get set to TRUE if so. If there are any
+ * SubLinks in the join alias lists, the outer Query should already have
+ * hasSubLinks = TRUE, so this is only relevant to un-flattened subqueries.
+ *
* NOTE: this is used on not-yet-planned expressions. We do not expect it
* to be applied directly to a Query node.
*/
@@ -698,6 +708,10 @@ flatten_join_alias_vars(PlannerInfo *root, Node *node)
context.root = root;
context.sublevels_up = 0;
+ /* flag whether join aliases could possibly contain SubLinks */
+ context.possible_sublink = root->parse->hasSubLinks;
+ /* if hasSubLinks is already true, no need to work hard */
+ context.inserted_sublink = root->parse->hasSubLinks;
return flatten_join_alias_vars_mutator(node, &context);
}
@@ -747,6 +761,7 @@ flatten_join_alias_vars_mutator(Node *node,
IncrementVarSublevelsUp(newvar, context->sublevels_up, 0);
}
/* Recurse in case join input is itself a join */
+ /* (also takes care of setting inserted_sublink if needed) */
newvar = flatten_join_alias_vars_mutator(newvar, context);
fields = lappend(fields, newvar);
}
@@ -773,8 +788,15 @@ flatten_join_alias_vars_mutator(Node *node,
newvar = copyObject(newvar);
IncrementVarSublevelsUp(newvar, context->sublevels_up, 0);
}
+
/* Recurse in case join input is itself a join */
- return flatten_join_alias_vars_mutator(newvar, context);
+ newvar = flatten_join_alias_vars_mutator(newvar, context);
+
+ /* Detect if we are adding a sublink to query */
+ if (context->possible_sublink && !context->inserted_sublink)
+ context->inserted_sublink = checkExprHasSubLink(newvar);
+
+ return newvar;
}
if (IsA(node, PlaceHolderVar))
{
@@ -797,12 +819,17 @@ flatten_join_alias_vars_mutator(Node *node,
{
/* Recurse into RTE subquery or not-yet-planned sublink subquery */
Query *newnode;
+ bool save_inserted_sublink;
context->sublevels_up++;
+ save_inserted_sublink = context->inserted_sublink;
+ context->inserted_sublink = ((Query *) node)->hasSubLinks;
newnode = query_tree_mutator((Query *) node,
flatten_join_alias_vars_mutator,
(void *) context,
QTW_IGNORE_JOINALIASES);
+ newnode->hasSubLinks |= context->inserted_sublink;
+ context->inserted_sublink = save_inserted_sublink;
context->sublevels_up--;
return (Node *) newnode;
}
diff --git a/src/test/regress/expected/subselect.out b/src/test/regress/expected/subselect.out
index b0b260f1847..e839ad7f964 100644
--- a/src/test/regress/expected/subselect.out
+++ b/src/test/regress/expected/subselect.out
@@ -507,3 +507,17 @@ select (select (a.*)::text) from view_a a;
(42)
(1 row)
+--
+-- Test case for sublinks pushed down into subselects via join alias expansion
+--
+select
+ (select sq1) as qq1
+from
+ (select exists(select 1 from int4_tbl where f1 = q2) as sq1, 42 as dummy
+ from int8_tbl) sq0
+ join
+ int4_tbl i4 on dummy = i4.f1;
+ qq1
+-----
+(0 rows)
+
diff --git a/src/test/regress/sql/subselect.sql b/src/test/regress/sql/subselect.sql
index 45be164d1d1..f6657fa535c 100644
--- a/src/test/regress/sql/subselect.sql
+++ b/src/test/regress/sql/subselect.sql
@@ -323,3 +323,15 @@ select view_a from view_a;
select (select view_a) from view_a;
select (select (select view_a)) from view_a;
select (select (a.*)::text) from view_a a;
+
+--
+-- Test case for sublinks pushed down into subselects via join alias expansion
+--
+
+select
+ (select sq1) as qq1
+from
+ (select exists(select 1 from int4_tbl where f1 = q2) as sq1, 42 as dummy
+ from int8_tbl) sq0
+ join
+ int4_tbl i4 on dummy = i4.f1;
--
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