Fix NULL start value handling in CAgg refresh

The CAgg refresh job did not handle the NULL value of start_offset for a
time_bucket function with a variable width properly. This problem has
led to the creation of invalid invalidation records and 'timestamp out
of range' errors during the next refresh.

Fixes: #5474

.unreleased/bugfix_6729

@@ -0,0 +1 @@
+Fixes: #6729 Fix NULL start value handling in CAgg refresh

tsl/src/bgw_policy/continuous_aggregate_api.c

@@ -111,13 +111,20 @@ get_time_from_config(const Dimension *dim, const Jsonb *config, const char *json
 }
 
 int64
-policy_refresh_cagg_get_refresh_start(const Dimension *dim, const Jsonb *config, bool *start_isnull)
+policy_refresh_cagg_get_refresh_start(const ContinuousAgg *cagg, const Dimension *dim,
+									  const Jsonb *config, bool *start_isnull)
 {
 	int64 res = get_time_from_config(dim, config, POL_REFRESH_CONF_KEY_START_OFFSET, start_isnull);
 
 	/* interpret NULL as min value for that type */
 	if (*start_isnull)
-		return ts_time_get_min(ts_dimension_get_partition_type(dim));
+	{
+		Oid type = ts_dimension_get_partition_type(dim);
+
+		return ts_continuous_agg_bucket_width_variable(cagg) ? ts_time_get_nobegin_or_min(type) :
+															   ts_time_get_min(type);
+	}
+
 	return res;
 }
 

tsl/src/bgw_policy/continuous_aggregate_api.h

@@ -16,8 +16,8 @@ extern Datum policy_refresh_cagg_check(PG_FUNCTION_ARGS);
 extern Datum policy_refresh_cagg_remove(PG_FUNCTION_ARGS);
 
 int32 policy_continuous_aggregate_get_mat_hypertable_id(const Jsonb *config);
-int64 policy_refresh_cagg_get_refresh_start(const Dimension *dim, const Jsonb *config,
-											bool *start_isnull);
+int64 policy_refresh_cagg_get_refresh_start(const ContinuousAgg *cagg, const Dimension *dim,
+											const Jsonb *config, bool *start_isnull);
 int64 policy_refresh_cagg_get_refresh_end(const Dimension *dim, const Jsonb *config,
 										  bool *end_isnull);
 bool policy_refresh_cagg_refresh_start_lt(int32 materialization_id, Oid cmp_type,

tsl/src/bgw_policy/job.c

@@ -401,9 +401,11 @@ policy_refresh_cagg_read_and_validate_config(Jsonb *config, PolicyContinuousAggD
 				 errmsg("configuration materialization hypertable id %d not found",
 						materialization_id)));
 
+	ContinuousAgg *cagg = ts_continuous_agg_find_by_mat_hypertable_id(materialization_id, false);
+
 	open_dim = get_open_dimension_for_hypertable(mat_ht, true);
 	dim_type = ts_dimension_get_partition_type(open_dim);
-	refresh_start = policy_refresh_cagg_get_refresh_start(open_dim, config, &start_isnull);
+	refresh_start = policy_refresh_cagg_get_refresh_start(cagg, open_dim, config, &start_isnull);
 	refresh_end = policy_refresh_cagg_get_refresh_end(open_dim, config, &end_isnull);
 
 	if (refresh_start >= refresh_end)
@@ -420,7 +422,7 @@ policy_refresh_cagg_read_and_validate_config(Jsonb *config, PolicyContinuousAggD
 		policy_data->refresh_window.type = dim_type;
 		policy_data->refresh_window.start = refresh_start;
 		policy_data->refresh_window.end = refresh_end;
-		policy_data->cagg = ts_continuous_agg_find_by_mat_hypertable_id(materialization_id, false);
+		policy_data->cagg = cagg;
 		policy_data->start_is_null = start_isnull;
 		policy_data->end_is_null = end_isnull;
 	}

tsl/test/expected/cagg_invalidation.out

@@ -1189,7 +1189,7 @@ WHERE cagg_id = :cond_10_id;
 
 -- should trigger two individual refreshes
 CALL refresh_continuous_aggregate('cond_10', 0, 200);
--- Allow at most 5 individual invalidations per refreshe
+-- Allow at most 5 individual invalidations per refresh
 SET timescaledb.materializations_per_refresh_window=5;
 -- Insert into every second bucket
 INSERT INTO conditions VALUES (20, 1, 1.0);
@@ -1226,6 +1226,7 @@ CALL refresh_continuous_aggregate('cond_10', 0, 200);
 WARNING:  invalid value for session variable "timescaledb.materializations_per_refresh_window"
 DETAIL:  Expected an integer but current value is "-".
 \set VERBOSITY terse
+RESET timescaledb.materializations_per_refresh_window;
 -- Test refresh with undefined invalidation threshold and variable sized buckets
 CREATE TABLE timestamp_ht (
   time timestamptz NOT NULL,
@@ -1275,3 +1276,41 @@ CREATE MATERIALIZED VIEW temperature_1month_hierarchical_ts
     FROM temperature_4h_2
     GROUP BY 1 ORDER BY 1;
 NOTICE:  continuous aggregate "temperature_1month_hierarchical_ts" is already up-to-date
+---------------------------------------------------------------------
+--- Issue 5474
+---------------------------------------------------------------------
+CREATE TABLE i5474 (
+time timestamptz NOT NULL,
+sensor_id integer NOT NULL,
+cpu double precision NOT NULL,
+temperature double precision NOT NULL);
+SELECT create_hypertable('i5474','time');
+  create_hypertable  
+---------------------
+ (16,public,i5474,t)
+(1 row)
+
+CREATE MATERIALIZED VIEW i5474_summary_daily
+    WITH (timescaledb.continuous) AS
+        SELECT
+            time_bucket('1 hour', time, 'AWST') AS bucket,
+            sensor_id,
+            avg(cpu) AS avg_cpu
+        FROM i5474
+        GROUP BY bucket, sensor_id;
+NOTICE:  continuous aggregate "i5474_summary_daily" is already up-to-date
+SELECT add_continuous_aggregate_policy('i5474_summary_daily',
+    start_offset      => NULL,
+    end_offset        => INTERVAL '10 MINUTES',
+    schedule_interval => INTERVAL '1 MINUTE'
+) new_job_id \gset
+-- Check that start_offset = NULL is handled properly by the refresh job...
+CALL run_job(:new_job_id);
+-- ...and the CAgg can be refreshed afterward
+CALL refresh_continuous_aggregate('i5474_summary_daily', NULL, '2023-03-21 05:00:00+00');
+NOTICE:  continuous aggregate "i5474_summary_daily" is already up-to-date
+INSERT INTO i5474 (time, sensor_id, cpu, temperature) VALUES ('2000-01-01 05:00:00+00', 1, 1.0, 1.0);
+CALL refresh_continuous_aggregate('i5474_summary_daily', NULL, '2023-01-01 01:00:00+00');
+-- CAgg should be up-to-date now
+CALL refresh_continuous_aggregate('i5474_summary_daily', NULL, '2023-01-01 01:00:00+00');
+NOTICE:  continuous aggregate "i5474_summary_daily" is already up-to-date

tsl/test/sql/cagg_invalidation.sql

@@ -683,7 +683,7 @@ WHERE cagg_id = :cond_10_id;
 -- should trigger two individual refreshes
 CALL refresh_continuous_aggregate('cond_10', 0, 200);
 
--- Allow at most 5 individual invalidations per refreshe
+-- Allow at most 5 individual invalidations per refresh
 SET timescaledb.materializations_per_refresh_window=5;
 
 -- Insert into every second bucket
@@ -719,6 +719,7 @@ SET timescaledb.materializations_per_refresh_window='-';
 INSERT INTO conditions VALUES (140, 1, 1.0);
 CALL refresh_continuous_aggregate('cond_10', 0, 200);
 \set VERBOSITY terse
+RESET timescaledb.materializations_per_refresh_window;
 
 -- Test refresh with undefined invalidation threshold and variable sized buckets
 CREATE TABLE timestamp_ht (
@@ -765,3 +766,40 @@ CREATE MATERIALIZED VIEW temperature_1month_hierarchical_ts
   SELECT time_bucket('1 month', bucket_4h, 'Europe/Berlin'), avg(average)
     FROM temperature_4h_2
     GROUP BY 1 ORDER BY 1;
+
+---------------------------------------------------------------------
+--- Issue 5474
+---------------------------------------------------------------------
+CREATE TABLE i5474 (
+time timestamptz NOT NULL,
+sensor_id integer NOT NULL,
+cpu double precision NOT NULL,
+temperature double precision NOT NULL);
+
+SELECT create_hypertable('i5474','time');
+
+CREATE MATERIALIZED VIEW i5474_summary_daily
+    WITH (timescaledb.continuous) AS
+        SELECT
+            time_bucket('1 hour', time, 'AWST') AS bucket,
+            sensor_id,
+            avg(cpu) AS avg_cpu
+        FROM i5474
+        GROUP BY bucket, sensor_id;
+
+SELECT add_continuous_aggregate_policy('i5474_summary_daily',
+    start_offset      => NULL,
+    end_offset        => INTERVAL '10 MINUTES',
+    schedule_interval => INTERVAL '1 MINUTE'
+) new_job_id \gset
+
+-- Check that start_offset = NULL is handled properly by the refresh job...
+CALL run_job(:new_job_id);
+
+-- ...and the CAgg can be refreshed afterward
+CALL refresh_continuous_aggregate('i5474_summary_daily', NULL, '2023-03-21 05:00:00+00');
+INSERT INTO i5474 (time, sensor_id, cpu, temperature) VALUES ('2000-01-01 05:00:00+00', 1, 1.0, 1.0);
+CALL refresh_continuous_aggregate('i5474_summary_daily', NULL, '2023-01-01 01:00:00+00');
+
+-- CAgg should be up-to-date now
+CALL refresh_continuous_aggregate('i5474_summary_daily', NULL, '2023-01-01 01:00:00+00');