Track nesting depth correctly when drilling down into RECORD Vars.

expandRecordVariable() failed to adjust the parse nesting structure
correctly when recursing to inspect an outer-level Var.  This could
result in assertion failures or core dumps in corner cases.

Likewise, get_name_for_var_field() failed to adjust the deparse
namespace stack correctly when recursing to inspect an outer-level
Var.  In this case the likely result was a "bogus varno" error
while deparsing a view.

Per bug #18077 from Jingzhou Fu.  Back-patch to all supported
branches.

Richard Guo, with some adjustments by me

Discussion: https://postgr.es/m/18077-b9db97c6e0ab45d8@postgresql.org

Author: tglsfdc

src/backend/parser/parse_target.c

@@ -1499,7 +1499,8 @@ ExpandRowReference(ParseState *pstate, Node *expr,
  * drill down to find the ultimate defining expression and attempt to infer
  * the tupdesc from it.  We ereport if we can't determine the tupdesc.
  *
- * levelsup is an extra offset to interpret the Var's varlevelsup correctly.
+ * levelsup is an extra offset to interpret the Var's varlevelsup correctly
+ * when recursing.  Outside callers should pass zero.
  */
 TupleDesc
 expandRecordVariable(ParseState *pstate, Var *var, int levelsup)
@@ -1587,10 +1588,17 @@ expandRecordVariable(ParseState *pstate, Var *var, int levelsup)
 					/*
 					 * Recurse into the sub-select to see what its Var refers
 					 * to.  We have to build an additional level of ParseState
-					 * to keep in step with varlevelsup in the subselect.
+					 * to keep in step with varlevelsup in the subselect;
+					 * furthermore, the subquery RTE might be from an outer
+					 * query level, in which case the ParseState for the
+					 * subselect must have that outer level as parent.
 					 */
 					ParseState	mypstate = {0};
+					Index		levelsup;
 
+					/* this loop must work, since GetRTEByRangeTablePosn did */
+					for (levelsup = 0; levelsup < netlevelsup; levelsup++)
+						pstate = pstate->parentParseState;
 					mypstate.parentParseState = pstate;
 					mypstate.p_rtable = rte->subquery->rtable;
 					/* don't bother filling the rest of the fake pstate */
@@ -1641,12 +1649,11 @@ expandRecordVariable(ParseState *pstate, Var *var, int levelsup)
 					 * Recurse into the CTE to see what its Var refers to. We
 					 * have to build an additional level of ParseState to keep
 					 * in step with varlevelsup in the CTE; furthermore it
-					 * could be an outer CTE.
+					 * could be an outer CTE (compare SUBQUERY case above).
 					 */
-					ParseState	mypstate;
+					ParseState	mypstate = {0};
 					Index		levelsup;
 
-					MemSet(&mypstate, 0, sizeof(mypstate));
 					/* this loop must work, since GetCTEForRTE did */
 					for (levelsup = 0;
 						 levelsup < rte->ctelevelsup + netlevelsup;

src/backend/utils/adt/ruleutils.c

@@ -7820,22 +7820,28 @@ get_name_for_var_field(Var *var, int fieldno,
 						 * Recurse into the sub-select to see what its Var
 						 * refers to. We have to build an additional level of
 						 * namespace to keep in step with varlevelsup in the
-						 * subselect.
+						 * subselect; furthermore, the subquery RTE might be
+						 * from an outer query level, in which case the
+						 * namespace for the subselect must have that outer
+						 * level as parent namespace.
 						 */
+						List	   *save_nslist = context->namespaces;
+						List	   *parent_namespaces;
 						deparse_namespace mydpns;
 						const char *result;
 
+						parent_namespaces = list_copy_tail(context->namespaces,
+														   netlevelsup);
+
 						set_deparse_for_query(&mydpns, rte->subquery,
-											  context->namespaces);
+											  parent_namespaces);
 
-						context->namespaces = lcons(&mydpns,
-													context->namespaces);
+						context->namespaces = lcons(&mydpns, parent_namespaces);
 
 						result = get_name_for_var_field((Var *) expr, fieldno,
 														0, context);
 
-						context->namespaces =
-							list_delete_first(context->namespaces);
+						context->namespaces = save_nslist;
 
 						return result;
 					}
@@ -7927,29 +7933,30 @@ get_name_for_var_field(Var *var, int fieldno,
 														attnum);
 
 					if (ste == NULL || ste->resjunk)
-						elog(ERROR, "subquery %s does not have attribute %d",
+						elog(ERROR, "CTE %s does not have attribute %d",
 							 rte->eref->aliasname, attnum);
 					expr = (Node *) ste->expr;
 					if (IsA(expr, Var))
 					{
 						/*
 						 * Recurse into the CTE to see what its Var refers to.
 						 * We have to build an additional level of namespace
-						 * to keep in step with varlevelsup in the CTE.
-						 * Furthermore it could be an outer CTE, so we may
-						 * have to delete some levels of namespace.
+						 * to keep in step with varlevelsup in the CTE;
+						 * furthermore it could be an outer CTE (compare
+						 * SUBQUERY case above).
 						 */
 						List	   *save_nslist = context->namespaces;
-						List	   *new_nslist;
+						List	   *parent_namespaces;
 						deparse_namespace mydpns;
 						const char *result;
 
+						parent_namespaces = list_copy_tail(context->namespaces,
+														   ctelevelsup);
+
 						set_deparse_for_query(&mydpns, ctequery,
-											  context->namespaces);
+											  parent_namespaces);
 
-						new_nslist = list_copy_tail(context->namespaces,
-													ctelevelsup);
-						context->namespaces = lcons(&mydpns, new_nslist);
+						context->namespaces = lcons(&mydpns, parent_namespaces);
 
 						result = get_name_for_var_field((Var *) expr, fieldno,
 														0, context);

src/test/regress/expected/rowtypes.out

@@ -1240,6 +1240,66 @@ select r, r is null as isnull, r is not null as isnotnull from r;
  (,)         | t      | f
 (6 rows)
 
+--
+-- Check parsing of indirect references to composite values (bug #18077)
+--
+explain (verbose, costs off)
+with cte(c) as materialized (select row(1, 2)),
+     cte2(c) as (select * from cte)
+select * from cte2 as t
+where (select * from (select c as c1) s
+       where (select (c1).f1 > 0)) is not null;
+                 QUERY PLAN                 
+--------------------------------------------
+ CTE Scan on cte
+   Output: cte.c
+   Filter: ((SubPlan 3) IS NOT NULL)
+   CTE cte
+     ->  Result
+           Output: '(1,2)'::record
+   SubPlan 3
+     ->  Result
+           Output: cte.c
+           One-Time Filter: $2
+           InitPlan 2 (returns $2)
+             ->  Result
+                   Output: ((cte.c).f1 > 0)
+(13 rows)
+
+with cte(c) as materialized (select row(1, 2)),
+     cte2(c) as (select * from cte)
+select * from cte2 as t
+where (select * from (select c as c1) s
+       where (select (c1).f1 > 0)) is not null;
+   c   
+-------
+ (1,2)
+(1 row)
+
+-- Also check deparsing of such cases
+create view composite_v as
+with cte(c) as materialized (select row(1, 2)),
+     cte2(c) as (select * from cte)
+select 1 as one from cte2 as t
+where (select * from (select c as c1) s
+       where (select (c1).f1 > 0)) is not null;
+select pg_get_viewdef('composite_v', true);
+                     pg_get_viewdef                     
+--------------------------------------------------------
+  WITH cte(c) AS MATERIALIZED (                        +
+          SELECT ROW(1, 2) AS "row"                    +
+         ), cte2(c) AS (                               +
+          SELECT cte.c                                 +
+            FROM cte                                   +
+         )                                             +
+  SELECT 1 AS one                                      +
+    FROM cte2 t                                        +
+   WHERE (( SELECT s.c1                                +
+            FROM ( SELECT t.c AS c1) s                 +
+           WHERE ( SELECT (s.c1).f1 > 0))) IS NOT NULL;
+(1 row)
+
+drop view composite_v;
 --
 -- Tests for component access / FieldSelect
 --

src/test/regress/sql/rowtypes.sql

@@ -494,6 +494,31 @@ with r(a,b) as materialized
           (null,row(1,2)), (null,row(null,null)), (null,null) )
 select r, r is null as isnull, r is not null as isnotnull from r;
 
+--
+-- Check parsing of indirect references to composite values (bug #18077)
+--
+explain (verbose, costs off)
+with cte(c) as materialized (select row(1, 2)),
+     cte2(c) as (select * from cte)
+select * from cte2 as t
+where (select * from (select c as c1) s
+       where (select (c1).f1 > 0)) is not null;
+
+with cte(c) as materialized (select row(1, 2)),
+     cte2(c) as (select * from cte)
+select * from cte2 as t
+where (select * from (select c as c1) s
+       where (select (c1).f1 > 0)) is not null;
+
+-- Also check deparsing of such cases
+create view composite_v as
+with cte(c) as materialized (select row(1, 2)),
+     cte2(c) as (select * from cte)
+select 1 as one from cte2 as t
+where (select * from (select c as c1) s
+       where (select (c1).f1 > 0)) is not null;
+select pg_get_viewdef('composite_v', true);
+drop view composite_v;
 
 --
 -- Tests for component access / FieldSelect