Allow changing real-time flag on deprecated CAggs

PR timescale#6798 prevents the usage of time_bucket_ng in CAgg definitions.
However, flipping the real-time functionality should still be possible.

tsl/src/continuous_aggs/common.c

@@ -256,8 +256,13 @@ caggtimebucket_validate(CAggTimebucketInfo *tbinfo, List *groupClause, List *tar
 				continue;
 			}
 
-			/* Do we have a bucketing function that is not allowed in the CAgg definition */
-			if (!function_allowed_in_cagg_definition(fe->funcid))
+			/* Do we have a bucketing function that is not allowed in the CAgg definition?
+			 *
+			 * This is only validated upon creation. If an older TSDB version has allowed us to use
+			 * the function and it's now removed from the list of allowed functions, we should not
+			 * error out (e.g., materialized_only setting is changed on a CAgg that uses the
+			 * deprecated time_bucket_ng function). */
+			if (is_cagg_create && !function_allowed_in_cagg_definition(fe->funcid))
 			{
 				if (IS_DEPRECATED_BUCKET_FUNC(finfo))
 				{

tsl/src/continuous_aggs/create.c

@@ -1026,7 +1026,7 @@ cagg_flip_realtime_view_definition(ContinuousAgg *agg, Hypertable *mat_ht)
 							agg->data.finalized,
 							NameStr(agg->data.user_view_schema),
 							NameStr(agg->data.user_view_name),
-							true);
+							false);
 
 	/* Flip */
 	agg->data.materialized_only = !agg->data.materialized_only;

tsl/src/continuous_aggs/repair.c

@@ -130,7 +130,7 @@ cagg_rebuild_view_definition(ContinuousAgg *agg, Hypertable *mat_ht, bool force_
 							finalized,
 							NameStr(agg->data.user_view_schema),
 							NameStr(agg->data.user_view_name),
-							true);
+							false);
 
 	mattablecolumninfo_init(&mattblinfo, copyObject(direct_query->groupClause));
 	fqi.finalized = finalized;

tsl/test/expected/exp_cagg_next_gen.out

@@ -196,5 +196,8 @@ FROM _timescaledb_catalog.continuous_aggs_bucket_function ORDER BY 1;
  timescaledb_experimental.time_bucket_ng(interval,timestamp without time zone) | @ 1 mon      |               |                 | f
 (2 rows)
 
+-- Try to toggle realtime feature on existing CAgg using timescaledb_experimental.time_bucket_ng
+ALTER MATERIALIZED VIEW conditions_summary_monthly SET (timescaledb.materialized_only=false);
+ALTER MATERIALIZED VIEW conditions_summary_monthly SET (timescaledb.materialized_only=true);
 \c :TEST_DBNAME :ROLE_SUPERUSER
 DROP DATABASE test WITH (FORCE);

tsl/test/sql/exp_cagg_next_gen.sql

@@ -163,5 +163,9 @@ WITH NO DATA;
 SELECT bucket_func, bucket_width, bucket_origin, bucket_timezone, bucket_fixed_width
 FROM _timescaledb_catalog.continuous_aggs_bucket_function ORDER BY 1;
 
+-- Try to toggle realtime feature on existing CAgg using timescaledb_experimental.time_bucket_ng
+ALTER MATERIALIZED VIEW conditions_summary_monthly SET (timescaledb.materialized_only=false);
+ALTER MATERIALIZED VIEW conditions_summary_monthly SET (timescaledb.materialized_only=true);
+
 \c :TEST_DBNAME :ROLE_SUPERUSER
 DROP DATABASE test WITH (FORCE);