Reset baserel cache on invalid hypertable cache

When popping the hypertable cache stack, it might happen that the
hypertable cache was invalidated between the push and the pop. In that
case, the baserel cache can contain invalid entries pointing to the now
popped hypertable cache, so we reset the baserel cache.

Fixes #4795

src/planner/planner.c

@@ -225,10 +225,16 @@ planner_hcache_pop(bool release)
 
 	hcache = linitial(planner_hcaches);
 
+	planner_hcaches = list_delete_first(planner_hcaches);
+
 	if (release)
+	{
 		ts_cache_release(hcache);
-
-	planner_hcaches = list_delete_first(planner_hcaches);
+		/* If we pop a stack and discover a new hypertable cache, the basrel
+		 * cache can contain invalid entries, so we reset it. */
+		if (planner_hcaches != NIL && hcache != linitial(planner_hcaches))
+			BaserelInfo_reset(ts_baserel_info);
+	}
 }
 
 static bool
@@ -457,6 +463,27 @@ timescaledb_planner(Query *parse, int cursor_opts, ParamListInfo bound_params)
 						"commands ignored until end of transaction block")));
 
 	planner_hcache_push();
+	if (ts_baserel_info == NULL)
+	{
+		/*
+		 * The calls to timescaledb_planner can be recursive (e.g. when
+		 * evaluating an immutable SQL function at planning time). We want to
+		 * create and destroy the per-query baserel info table only at the
+		 * top-level call, hence this flag.
+		 */
+		reset_baserel_info = true;
+
+		/*
+		 * This is a per-query cache, so we create it in the current memory
+		 * context for the top-level call of this function, which hopefully
+		 * should exist for the duration of the query. Message or portal
+		 * memory contexts could also be suitable, but they don't exist for
+		 * SPI calls.
+		 */
+		ts_baserel_info = BaserelInfo_create(CurrentMemoryContext,
+											 /* nelements = */ 1,
+											 /* private_data = */ NULL);
+	}
 
 	PG_TRY();
 	{
@@ -533,28 +560,6 @@ timescaledb_planner(Query *parse, int cursor_opts, ParamListInfo bound_params)
 					}
 				}
 			}
-
-			if (ts_baserel_info == NULL)
-			{
-				/*
-				 * The calls to timescaledb_planner can be recursive (e.g. when
-				 * evaluating an immutable SQL function at planning time). We
-				 * want to create and destroy the per-query baserel info table
-				 * only at the top-level call, hence this flag.
-				 */
-				reset_baserel_info = true;
-
-				/*
-				 * This is a per-query cache, so we create it in the current
-				 * memory context for the top-level call of this function, which
-				 * hopefully should exist for the duration of the query. Message
-				 * or portal memory contexts could also be suitable, but they
-				 * don't exist for SPI calls.
-				 */
-				ts_baserel_info = BaserelInfo_create(CurrentMemoryContext,
-													 /* nelements = */ 1,
-													 /* private_data = */ NULL);
-			}
 		}
 
 		if (prev_planner_hook != NULL)
@@ -957,9 +962,9 @@ reenable_inheritance(PlannerInfo *root, RelOptInfo *rel, Index rti, RangeTblEntr
 
 			in_rte->inh = true;
 			reenabled_inheritance = true;
-			/* Redo set_rel_consider_parallel, as results of the call may no longer be valid here
-			 * (due to adding more tables to the set of tables under consideration here). This is
-			 * especially true if dealing with foreign data wrappers. */
+			/* Redo set_rel_consider_parallel, as results of the call may no longer be valid
+			 * here (due to adding more tables to the set of tables under consideration here).
+			 * This is especially true if dealing with foreign data wrappers. */
 
 			/*
 			 * An entry of reloptkind RELOPT_OTHER_MEMBER_REL might still