Deprecate continuous aggregates with old format

This patch will report a warning when upgrading to new timescaledb
extension. Also restrict users from creating cagss with old format
on timescaledb with PG15.

sql/updates/post-update.sql

@@ -132,3 +132,19 @@ FROM _timescaledb_catalog.hypertable h
 INNER JOIN _timescaledb_catalog.dimension d ON (d.hypertable_id = h.id)
 WHERE d.interval_length IS NULL; 
 DROP FUNCTION _timescaledb_internal.update_dimension_partition;
+
+-- Report warning when partial aggregates are used
+DO $$
+DECLARE
+  cagg_cnt int := 0;
+BEGIN
+  IF current_setting('server_version_num')::int >  140000 THEN
+      SELECT
+        COUNT(*) INTO cagg_cnt
+      FROM _timescaledb_catalog.continuous_agg cagg
+      WHERE cagg.finalized = false;
+  END IF;
+  IF cagg_cnt > 0 THEN
+    RAISE WARNING 'Continuous Aggregates with old format will not be supported with PG15. You should upgrade to the new format';
+  END IF;
+END $$;

tsl/src/continuous_aggs/create.c

@@ -1055,6 +1055,19 @@ cagg_query_supported(Query *query, StringInfo hint, StringInfo detail, const boo
 		return false;
 	}
 
+#if PG15_GE
+	if (!finalized)
+	{
+		/* continuous aggregates with old format will not be allowed */
+		appendStringInfoString(detail,
+							   "Continuous aggregates with partials will not be supported.");
+		appendStringInfoString(hint,
+							   "Define Continuous aggregates with finalized parameter set to "
+							   "true.");
+		return false;
+	}
+#endif
+
 	return true; /* Query was OK and is supported */
 }