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

1 files changed, 22 insertions, 15 deletions

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 97b0ef22ac5..68f301484e3 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/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;
 					}
@@ -7927,7 +7933,7 @@ 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))
@@ -7935,21 +7941,22 @@ get_name_for_var_field(Var *var, int fieldno,
 						/*
 						 * 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);