Calculate agglevelsup correctly when Aggref contains a CTE.

If an aggregate function call contains a sub-select that has
an RTE referencing a CTE outside the aggregate, we must treat
that reference like a Var referencing the CTE's query level
for purposes of determining the aggregate's level.  Otherwise
we might reach the nonsensical conclusion that the aggregate
should be evaluated at some query level higher than the CTE,
ending in a planner error or a broken plan tree that causes
executor failures.

Bug: #19055
Reported-by: BugForge <dllggyx@outlook.com>
Author: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/19055-6970cfa8556a394d@postgresql.org
Backpatch-through: 13

diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c
index 6143d4a25553d079d498a316711b00b3ea8ac912..d0592a1176c2d86e9b881aca6beffacc09d678a3 100644 (file)
--- a/src/backend/parser/parse_agg.c
+++ b/src/backend/parser/parse_agg.c
@@ -776,6 +776,32 @@ check_agg_arguments_walker(Node *node,
                                         parser_errposition(context->pstate,
                                                                                ((WindowFunc *) node)->location)));
        }
+
+       if (IsA(node, RangeTblEntry))
+       {
+               /*
+                * CTE references act similarly to Vars of the CTE's level.  Without
+                * this we might conclude that the Agg can be evaluated above the CTE,
+                * leading to trouble.
+                */
+               RangeTblEntry *rte = (RangeTblEntry *) node;
+
+               if (rte->rtekind == RTE_CTE)
+               {
+                       int                     ctelevelsup = rte->ctelevelsup;
+
+                       /* convert levelsup to frame of reference of original query */
+                       ctelevelsup -= context->sublevels_up;
+                       /* ignore local CTEs of subqueries */
+                       if (ctelevelsup >= 0)
+                       {
+                               if (context->min_varlevel < 0 ||
+                                       context->min_varlevel > ctelevelsup)
+                                       context->min_varlevel = ctelevelsup;
+                       }
+               }
+               return false;                   /* allow range_table_walker to continue */
+       }
        if (IsA(node, Query))
        {
                /* Recurse into subselects */
@@ -785,7 +811,7 @@ check_agg_arguments_walker(Node *node,
                result = query_tree_walker((Query *) node,
                                                                   check_agg_arguments_walker,
                                                                   (void *) context,
-                                                                  0);
+                                                                  QTW_EXAMINE_RTES_BEFORE);
                context->sublevels_up--;
                return result;
        }

diff --git a/src/test/regress/expected/with.out b/src/test/regress/expected/with.out
index 84a775db17e54f86d53e6d2e7672d1deff161526..d7b431a9aa27bdfaed95636692faa5ffd906e815 100644 (file)
--- a/src/test/regress/expected/with.out
+++ b/src/test/regress/expected/with.out
@@ -2192,6 +2192,40 @@ from int4_tbl;
  -2147483647
 (5 rows)
 
+--
+-- test for bug #19055: interaction of WITH with aggregates
+--
+-- The reference to cte1 must determine the aggregate's level,
+-- even though it contains no Vars referencing cte1
+explain (verbose, costs off)
+select f1, (with cte1(x,y) as (select 1,2)
+            select count((select i4.f1 from cte1))) as ss
+from int4_tbl i4;
+            QUERY PLAN             
+-----------------------------------
+ Seq Scan on public.int4_tbl i4
+   Output: i4.f1, (SubPlan 2)
+   SubPlan 2
+     ->  Aggregate
+           Output: count($1)
+           InitPlan 1 (returns $1)
+             ->  Result
+                   Output: i4.f1
+           ->  Result
+(9 rows)
+
+select f1, (with cte1(x,y) as (select 1,2)
+            select count((select i4.f1 from cte1))) as ss
+from int4_tbl i4;
+     f1      | ss 
+-------------+----
+           0 |  1
+      123456 |  1
+     -123456 |  1
+  2147483647 |  1
+ -2147483647 |  1
+(5 rows)
+
 --
 -- test for nested-recursive-WITH bug
 --

diff --git a/src/test/regress/sql/with.sql b/src/test/regress/sql/with.sql
index e91d70311dbfc03282ca094737fa202a487f48c9..cd6ce45a4342d39eb029518386f911ed796fd2f1 100644 (file)
--- a/src/test/regress/sql/with.sql
+++ b/src/test/regress/sql/with.sql
@@ -1056,6 +1056,20 @@ select ( with cte(foo) as ( values(f1) )
           values((select foo from cte)) )
 from int4_tbl;
 
+--
+-- test for bug #19055: interaction of WITH with aggregates
+--
+-- The reference to cte1 must determine the aggregate's level,
+-- even though it contains no Vars referencing cte1
+explain (verbose, costs off)
+select f1, (with cte1(x,y) as (select 1,2)
+            select count((select i4.f1 from cte1))) as ss
+from int4_tbl i4;
+
+select f1, (with cte1(x,y) as (select 1,2)
+            select count((select i4.f1 from cte1))) as ss
+from int4_tbl i4;
+
 --
 -- test for nested-recursive-WITH bug
 --