Fix planner error with pulling up subquery expressions into function RTEs.

tglsfdc · tglsfdc · commit 4d5f651f1d65 · 2021-10-14T12:43:55.000-04:00
If a function-in-FROM laterally references the output of some sub-SELECT earlier in the FROM clause, and we are able to flatten that sub-SELECT into the outer query, the expression(s) copied into the function RTE missed being processed by eval_const_expressions. This'd lead to trouble and probable crashes at execution if such expressions contained named-argument function call syntax or functions with defaulted arguments. The bug is masked if the query contains any explicit JOIN syntax, which may help explain why we'd not noticed. Per bug #17227 from Bernd Dorn. This is an oversight in commit 7266d09, so back-patch to v13 where that came in. Discussion: https://postgr.es/m/17227-5a28ed1512189fa4@postgresql.org
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
@@ -1084,8 +1084,10 @@ preprocess_expression(PlannerInfo *root, Node *expr, int kind)
 
 	/*
 	 * Simplify constant expressions.  For function RTEs, this was already
-	 * done by preprocess_function_rtes ... but we have to do it again if the
-	 * RTE is LATERAL and might have contained join alias variables.
+	 * done by preprocess_function_rtes.  (But note we must do it again for
+	 * EXPRKIND_RTFUNC_LATERAL, because those might by now contain
+	 * un-simplified subexpressions inserted by flattening of subqueries or
+	 * join alias variables.)
 	 *
 	 * Note: an essential effect of this is to convert named-argument function
 	 * calls to positional notation and insert the current actual values of
@@ -1099,8 +1101,7 @@ preprocess_expression(PlannerInfo *root, Node *expr, int kind)
 	 * careful to maintain AND/OR flatness --- that is, do not generate a tree
 	 * with AND directly under AND, nor OR directly under OR.
 	 */
-	if (!(kind == EXPRKIND_RTFUNC ||
-		  (kind == EXPRKIND_RTFUNC_LATERAL && !root->hasJoinRTEs)))
+	if (kind != EXPRKIND_RTFUNC)
 		expr = eval_const_expressions(root, expr);
 
 	/*
diff --git a/src/test/regress/expected/rangefuncs.out b/src/test/regress/expected/rangefuncs.out
@@ -2416,3 +2416,32 @@ select *, row_to_json(u) from unnest(array[]::rngfunc2[]) u;
 (0 rows)
 
 drop type rngfunc2;
+-- check handling of functions pulled up into function RTEs (bug #17227)
+explain (verbose, costs off)
+select * from
+  (select jsonb_path_query_array(module->'lectures', '$[*]') as lecture
+   from unnest(array['{"lectures": [{"id": "1"}]}'::jsonb])
+        as unnested_modules(module)) as ss,
+  jsonb_to_recordset(ss.lecture) as j (id text);
+                                                                       QUERY PLAN                                                                       
+--------------------------------------------------------------------------------------------------------------------------------------------------------
+ Nested Loop
+   Output: jsonb_path_query_array((unnested_modules.module -> 'lectures'::text), '$[*]'::jsonpath, '{}'::jsonb, false), j.id
+   ->  Function Scan on pg_catalog.unnest unnested_modules
+         Output: unnested_modules.module
+         Function Call: unnest('{"{\"lectures\": [{\"id\": \"1\"}]}"}'::jsonb[])
+   ->  Function Scan on pg_catalog.jsonb_to_recordset j
+         Output: j.id
+         Function Call: jsonb_to_recordset(jsonb_path_query_array((unnested_modules.module -> 'lectures'::text), '$[*]'::jsonpath, '{}'::jsonb, false))
+(8 rows)
+
+select * from
+  (select jsonb_path_query_array(module->'lectures', '$[*]') as lecture
+   from unnest(array['{"lectures": [{"id": "1"}]}'::jsonb])
+        as unnested_modules(module)) as ss,
+  jsonb_to_recordset(ss.lecture) as j (id text);
+    lecture    | id 
+---------------+----
+ [{"id": "1"}] | 1
+(1 row)
+
diff --git a/src/test/regress/sql/rangefuncs.sql b/src/test/regress/sql/rangefuncs.sql
@@ -767,3 +767,18 @@ select *, row_to_json(u) from unnest(array[null::rngfunc2, (1,'foo')::rngfunc2,
 select *, row_to_json(u) from unnest(array[]::rngfunc2[]) u;
 
 drop type rngfunc2;
+
+-- check handling of functions pulled up into function RTEs (bug #17227)
+
+explain (verbose, costs off)
+select * from
+  (select jsonb_path_query_array(module->'lectures', '$[*]') as lecture
+   from unnest(array['{"lectures": [{"id": "1"}]}'::jsonb])
+        as unnested_modules(module)) as ss,
+  jsonb_to_recordset(ss.lecture) as j (id text);
+
+select * from
+  (select jsonb_path_query_array(module->'lectures', '$[*]') as lecture
+   from unnest(array['{"lectures": [{"id": "1"}]}'::jsonb])
+        as unnested_modules(module)) as ss,
+  jsonb_to_recordset(ss.lecture) as j (id text);
