Ensure that chunks are aligned.

Previously, chunks could end up unaligned betweeen partitions if the chunk_time_interval
was updated between chunk creations. Now there is a check when a chunk is created whether there is
a chunk matching the time point in another partition and if there is, the new chunk is created
with the same interval.

sql/chunk.sql

@@ -18,7 +18,7 @@ $BODY$;
 -- static
 CREATE OR REPLACE FUNCTION _timescaledb_internal.calculate_new_chunk_times(
         partition_id INT,
-        "time"       BIGINT,
+        time_point   BIGINT,
     OUT table_start  BIGINT,
     OUT table_end    BIGINT
 )
@@ -27,8 +27,11 @@ $BODY$
 DECLARE
     partition_epoch_row _timescaledb_catalog.partition_epoch;
     chunk_row           _timescaledb_catalog.chunk;
-    time_interval BIGINT;
+    time_interval       BIGINT;
+    start_distinct_ctn  BIGINT;
+    end_distinct_ctn    BIGINT;
 BEGIN
+
     SELECT pe.*
     INTO partition_epoch_row
     FROM _timescaledb_catalog.partition p
@@ -36,6 +39,37 @@ BEGIN
     WHERE p.id = partition_id
     FOR SHARE;
 
+    -- Check if there are chunks in other partitions.
+    -- If so, use their time range to keep chunks time aligned
+
+    SELECT COUNT(DISTINCT(start_time)), COUNT(DISTINCT(end_time))
+    INTO start_distinct_ctn, end_distinct_ctn
+    FROM _timescaledb_catalog.chunk c
+    INNER JOIN _timescaledb_catalog.partition p ON (p.id = c.partition_id)
+    WHERE c.start_time <= time_point AND
+          c.end_time >= time_point AND
+          p.epoch_id = partition_epoch_row.id;
+
+    -- Sanity check that all previous chunks between partitions are
+    -- aligned
+    IF start_distinct_ctn != 0 or end_distinct_ctn != 0 THEN
+        -- At least one chunk exists, check that all chunks 
+        -- from other partitions are aligned
+        IF start_distinct_ctn != 1 OR end_distinct_ctn != 1 THEN
+           RAISE EXCEPTION 'Unaligned chunks between partitions';
+        END IF;
+
+        SELECT start_time, end_time 
+        INTO table_start, table_end
+        FROM _timescaledb_catalog.chunk AS c
+        INNER JOIN _timescaledb_catalog.partition p ON (p.id = c.partition_id)
+        WHERE c.start_time <= time_point AND
+              c.end_time >= time_point AND
+              p.epoch_id = partition_epoch_row.id LIMIT 1;    
+
+        RETURN; 
+    END IF;
+
     SELECT chunk_time_interval
     INTO time_interval
     FROM _timescaledb_catalog.hypertable ht
@@ -43,7 +77,7 @@ BEGIN
 
     -- Create start and stop times for the new chunk, subtract 1 from the end time
     -- as chunk intervals are inclusive.
-    table_start := ("time" / time_interval) * time_interval;
+    table_start := (time_point / time_interval) * time_interval;
     table_end := table_start + time_interval - 1;
 
     -- Check whether the new chunk interval overlaps with existing chunks.
@@ -79,7 +113,8 @@ BEGIN
 END
 $BODY$;
 
--- creates the row in the chunk table. Prerequisite: appropriate lock.
+-- creates the row in the chunk table. Prerequisite: appropriate lock and check that chunk does not
+-- already exist.
 -- static
 CREATE OR REPLACE FUNCTION _timescaledb_internal.create_chunk_row(
     part_id     INT,
@@ -90,8 +125,8 @@ $BODY$
 DECLARE
     table_start BIGINT;
     table_end   BIGINT;
-BEGIN
+BEGIN    
-
+    
     SELECT *
     INTO table_start, table_end
     FROM _timescaledb_internal.calculate_new_chunk_times(part_id, time_point);
@@ -131,7 +166,7 @@ BEGIN
     END IF;
 
     IF chunk_row IS NULL THEN -- recheck
-        RAISE EXCEPTION 'Should never happen: chunk not found after creation on meta'
+        RAISE EXCEPTION 'Should never happen: chunk not found after creation'
         USING ERRCODE = 'IO501';
     END IF;
 

test/expected/create_chunks.out

@@ -78,3 +78,48 @@ SELECT * FROM _timescaledb_catalog.chunk c
   4 |            1 |         10 |       39 | _timescaledb_internal | _hyper_1_4_chunk |  1 |        1 |              0 |        16383 |            |  1 |             1 |            |          |              2 | _timescaledb_internal    | get_partition_for_key |            32768 | device_id           |  1 | public      | chunk_test | _timescaledb_internal  | _hyper_1                | time             | bigint           |                  40
 (4 rows)
 
+-- Test chunk aligning between partitions
+CREATE TABLE chunk_align_test(
+        time       BIGINT,
+        metric     INTEGER,
+        device_id  TEXT
+    );
+SELECT * FROM create_hypertable('chunk_align_test', 'time', 'device_id', 2, chunk_time_interval => 10);
+ create_hypertable 
+-------------------
+ 
+(1 row)
+
+INSERT INTO chunk_align_test VALUES (1, 1, 'dev1'); -- this should create a 10 wide chunk
+SELECT c.id,partition_id,c.start_time,c.end_time,h.table_name,p.epoch_id FROM _timescaledb_catalog.chunk c
+    LEFT JOIN _timescaledb_catalog.partition p ON (p.id = c.partition_id)
+    LEFT JOIN _timescaledb_catalog.partition_epoch pe ON (pe.id = p.epoch_id)
+    LEFT JOIN _timescaledb_catalog.hypertable h ON (pe.hypertable_id = h.id)
+    WHERE h.schema_name = 'public' AND h.table_name = 'chunk_align_test'
+    ORDER BY c.id;
+ id | partition_id | start_time | end_time |    table_name    | epoch_id 
+----+--------------+------------+----------+------------------+----------
+  5 |            3 |          0 |        9 | chunk_align_test |        2
+(1 row)
+
+SELECT * FROM set_chunk_time_interval('chunk_align_test', 40::bigint);
+ set_chunk_time_interval 
+-------------------------
+ 
+(1 row)
+
+INSERT INTO chunk_align_test VALUES (5, 1, 'dev2'); -- this should still create a 10 wide chunk
+INSERT INTO chunk_align_test VALUES (45, 1, 'dev2'); -- this should create a 40 wide chunk
+SELECT c.id,partition_id,c.start_time,c.end_time,h.table_name,p.epoch_id  FROM _timescaledb_catalog.chunk c
+    LEFT JOIN _timescaledb_catalog.partition p ON (p.id = c.partition_id)
+    LEFT JOIN _timescaledb_catalog.partition_epoch pe ON (pe.id = p.epoch_id)
+    LEFT JOIN _timescaledb_catalog.hypertable h ON (pe.hypertable_id = h.id)
+    WHERE h.schema_name = 'public' AND h.table_name = 'chunk_align_test'
+    ORDER BY c.id;
+ id | partition_id | start_time | end_time |    table_name    | epoch_id 
+----+--------------+------------+----------+------------------+----------
+  5 |            3 |          0 |        9 | chunk_align_test |        2
+  6 |            4 |          0 |        9 | chunk_align_test |        2
+  7 |            4 |         40 |       79 | chunk_align_test |        2
+(3 rows)
+

test/sql/create_chunks.sql

@@ -17,7 +17,6 @@ INSERT INTO chunk_test VALUES (1, 1, 'dev1'),
 
 SELECT * FROM set_chunk_time_interval('chunk_test', 40::bigint);
 
-
 INSERT INTO chunk_test VALUES(23, 3, 'dev3');
 
 SELECT * FROM chunk_test order by time, metric, device_id;
@@ -32,3 +31,31 @@ SELECT * FROM _timescaledb_catalog.chunk c
     WHERE h.schema_name = 'public' AND h.table_name = 'chunk_test'
     ORDER BY c.id;
 
+
+-- Test chunk aligning between partitions
+CREATE TABLE chunk_align_test(
+        time       BIGINT,
+        metric     INTEGER,
+        device_id  TEXT
+    );
+SELECT * FROM create_hypertable('chunk_align_test', 'time', 'device_id', 2, chunk_time_interval => 10);
+
+INSERT INTO chunk_align_test VALUES (1, 1, 'dev1'); -- this should create a 10 wide chunk
+
+SELECT c.id,partition_id,c.start_time,c.end_time,h.table_name,p.epoch_id FROM _timescaledb_catalog.chunk c
+    LEFT JOIN _timescaledb_catalog.partition p ON (p.id = c.partition_id)
+    LEFT JOIN _timescaledb_catalog.partition_epoch pe ON (pe.id = p.epoch_id)
+    LEFT JOIN _timescaledb_catalog.hypertable h ON (pe.hypertable_id = h.id)
+    WHERE h.schema_name = 'public' AND h.table_name = 'chunk_align_test'
+    ORDER BY c.id;
+
+SELECT * FROM set_chunk_time_interval('chunk_align_test', 40::bigint);
+INSERT INTO chunk_align_test VALUES (5, 1, 'dev2'); -- this should still create a 10 wide chunk
+INSERT INTO chunk_align_test VALUES (45, 1, 'dev2'); -- this should create a 40 wide chunk
+
+SELECT c.id,partition_id,c.start_time,c.end_time,h.table_name,p.epoch_id  FROM _timescaledb_catalog.chunk c
+    LEFT JOIN _timescaledb_catalog.partition p ON (p.id = c.partition_id)
+    LEFT JOIN _timescaledb_catalog.partition_epoch pe ON (pe.id = p.epoch_id)
+    LEFT JOIN _timescaledb_catalog.hypertable h ON (pe.hypertable_id = h.id)
+    WHERE h.schema_name = 'public' AND h.table_name = 'chunk_align_test'
+    ORDER BY c.id;