0002-bug-18576-fix-v2.patch

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 653685bffc..ab88355d9a 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -7895,17 +7895,29 @@ get_name_for_var_field(Var *var, int fieldno,
 					/*
 					 * We're deparsing a Plan tree so we don't have complete
 					 * RTE entries (in particular, rte->subquery is NULL). But
-					 * the only place we'd see a Var directly referencing a
-					 * SUBQUERY RTE is in a SubqueryScan plan node, and we can
-					 * look into the child plan's tlist instead.
+					 * the only place we'd normally see a Var directly
+					 * referencing a SUBQUERY RTE is in a SubqueryScan plan
+					 * node, and we can look into the child plan's tlist
+					 * instead.  An exception occurs if the subquery was
+					 * proven empty and optimized away: then we'd find such a
+					 * Var in a childless Result node, and there's nothing in
+					 * the plan tree that would let us figure out what it had
+					 * originally referenced.  In that case, fall back on
+					 * printing "fN", analogously to the default column names
+					 * for RowExprs.
 					 */
 					TargetEntry *tle;
 					deparse_namespace save_dpns;
 					const char *result;
 
 					if (!dpns->inner_plan)
-						elog(ERROR, "failed to find plan for subquery %s",
-							 rte->eref->aliasname);
+					{
+						char	   *dummyname = palloc(32);
+
+						snprintf(dummyname, 32, "f%d", fieldno);
+						return dummyname;
+					}
+
 					tle = get_tle_by_resno(dpns->inner_tlist, attnum);
 					if (!tle)
 						elog(ERROR, "bogus varattno for subquery var: %d",
@@ -8014,20 +8026,27 @@ get_name_for_var_field(Var *var, int fieldno,
 				{
 					/*
 					 * We're deparsing a Plan tree so we don't have a CTE
-					 * list.  But the only places we'd see a Var directly
-					 * referencing a CTE RTE are in CteScan or WorkTableScan
-					 * plan nodes.  For those cases, set_deparse_plan arranged
-					 * for dpns->inner_plan to be the plan node that emits the
-					 * CTE or RecursiveUnion result, and we can look at its
-					 * tlist instead.
+					 * list.  But the only places we'd normally see a Var
+					 * directly referencing a CTE RTE are in CteScan or
+					 * WorkTableScan plan nodes.  For those cases,
+					 * set_deparse_plan arranged for dpns->inner_plan to be
+					 * the plan node that emits the CTE or RecursiveUnion
+					 * result, and we can look at its tlist instead.  As
+					 * above, this can fail if the CTE has been proven empty,
+					 * in which case fall back to "fN".
 					 */
 					TargetEntry *tle;
 					deparse_namespace save_dpns;
 					const char *result;
 
 					if (!dpns->inner_plan)
-						elog(ERROR, "failed to find plan for CTE %s",
-							 rte->eref->aliasname);
+					{
+						char	   *dummyname = palloc(32);
+
+						snprintf(dummyname, 32, "f%d", fieldno);
+						return dummyname;
+					}
+
 					tle = get_tle_by_resno(dpns->inner_tlist, attnum);
 					if (!tle)
 						elog(ERROR, "bogus varattno for subquery var: %d",
diff --git a/src/test/regress/expected/rowtypes.out b/src/test/regress/expected/rowtypes.out
index b400b58f76..9168979a62 100644
--- a/src/test/regress/expected/rowtypes.out
+++ b/src/test/regress/expected/rowtypes.out
@@ -1300,6 +1300,60 @@ select pg_get_viewdef('composite_v', true);
 (1 row)
 
 drop view composite_v;
+--
+-- Check cases where the composite comes from a proven-dummy rel (bug #18576)
+--
+explain (verbose, costs off)
+select (ss.a).x, (ss.a).n from
+  (select information_schema._pg_expandarray(array[1,2]) AS a) ss;
+                               QUERY PLAN                               
+------------------------------------------------------------------------
+ Subquery Scan on ss
+   Output: (ss.a).x, (ss.a).n
+   ->  ProjectSet
+         Output: information_schema._pg_expandarray('{1,2}'::integer[])
+         ->  Result
+(5 rows)
+
+explain (verbose, costs off)
+select (ss.a).x, (ss.a).n from
+  (select information_schema._pg_expandarray(array[1,2]) AS a) ss
+where false;
+        QUERY PLAN        
+--------------------------
+ Result
+   Output: (a).f1, (a).f2
+   One-Time Filter: false
+(3 rows)
+
+explain (verbose, costs off)
+with cte(c) as materialized (select row(1, 2)),
+     cte2(c) as (select * from cte)
+select (c).f1 from cte2 as t;
+            QUERY PLAN             
+-----------------------------------
+ CTE Scan on cte
+   Output: (cte.c).f1
+   CTE cte
+     ->  Result
+           Output: '(1,2)'::record
+(5 rows)
+
+explain (verbose, costs off)
+with cte(c) as materialized (select row(1, 2)),
+     cte2(c) as (select * from cte)
+select (c).f1 from cte2 as t
+where false;
+            QUERY PLAN             
+-----------------------------------
+ Result
+   Output: (cte.c).f1
+   One-Time Filter: false
+   CTE cte
+     ->  Result
+           Output: '(1,2)'::record
+(6 rows)
+
 --
 -- Tests for component access / FieldSelect
 --
diff --git a/src/test/regress/sql/rowtypes.sql b/src/test/regress/sql/rowtypes.sql
index fd47dc9e0f..174b062144 100644
--- a/src/test/regress/sql/rowtypes.sql
+++ b/src/test/regress/sql/rowtypes.sql
@@ -520,6 +520,27 @@ where (select * from (select c as c1) s
 select pg_get_viewdef('composite_v', true);
 drop view composite_v;
 
+--
+-- Check cases where the composite comes from a proven-dummy rel (bug #18576)
+--
+explain (verbose, costs off)
+select (ss.a).x, (ss.a).n from
+  (select information_schema._pg_expandarray(array[1,2]) AS a) ss;
+explain (verbose, costs off)
+select (ss.a).x, (ss.a).n from
+  (select information_schema._pg_expandarray(array[1,2]) AS a) ss
+where false;
+
+explain (verbose, costs off)
+with cte(c) as materialized (select row(1, 2)),
+     cte2(c) as (select * from cte)
+select (c).f1 from cte2 as t;
+explain (verbose, costs off)
+with cte(c) as materialized (select row(1, 2)),
+     cte2(c) as (select * from cte)
+select (c).f1 from cte2 as t
+where false;
+
 --
 -- Tests for component access / FieldSelect
 --