If you are running Timescale on your own hardware, you can save storage by moving chunks between tablespaces. By moving older chunks to cheaper, slower storage, you can save on storage costs while still using faster, more expensive storage for frequently accessed data. Moving infrequently accessed chunks can also improve performance, because it isolates historical data from the continual read-and-write workload of more recent data.
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To move chunks to a new tablespace, you first need to create the new tablespace
and set the storage mount point. You can then use the
move_chunk API call to move individual chunks from the
default tablespace to the new tablespace. The
move_chunk command also allows
you to move indexes belonging to those chunks to an appropriate tablespace.
move_chunk allows you reorder the chunk during the migration.
This can be used to make your queries faster, and works in a similar way to the
You must be logged in as a super user, such as the
postgres user, to use the
move_chunk() API call.
Create a new tablespace. In this example, the tablespace is called
history, it is owned by the
postgressuper user, and the mount point is
/mnt/history:CREATE TABLESPACE historyOWNER postgresLOCATION '/mnt/history';
List chunks that you want to move. In this example, chunks that contain data that is older than two days:SELECT show_chunks('conditions', older_than => INTERVAL '2 days');
Move a chunk and its index to the new tablespace. You can also reorder the data in this step. In this example, the chunk called
_timescaledb_internal._hyper_1_4_chunkis moved to the
historytablespace, and is reordered based on its time index:SELECT move_chunk(chunk => '_timescaledb_internal._hyper_1_4_chunk',destination_tablespace => 'history',index_destination_tablespace => 'history',reorder_index => '_timescaledb_internal._hyper_1_4_chunk_netdata_time_idx',verbose => TRUE);
You can verify that the chunk now resides in the correct tablespace by querying
pg_tablesto list all of the chunks on the tablespace:SELECT tablename from pg_tablesWHERE tablespace = 'history' and tablename like '_hyper_%_%_chunk';
You can also verify that the index is in the correct location:SELECT indexname FROM pg_indexes WHERE tablespace = 'history';
To move several chunks at once, select the chunks you want to move by using
FROM show_chunks(...). For example, to move chunks containing data between 1
and 3 weeks old, in a hypertable named
SELECT move_chunk(chunk => i,destination_tablespace => '<TABLESPACE>')FROM show_chunks('example', now() - INTERVAL '1 week', now() - INTERVAL '3 weeks') i;
After moving a chunk to a slower tablespace, you can move it back to the default, faster tablespace:
SELECT move_chunk(chunk => '_timescaledb_internal._hyper_1_4_chunk',destination_tablespace => 'pg_default',index_destination_tablespace => 'pg_default',reorder_index => '_timescaledb_internal._hyper_1_4_chunk_netdata_time_idx');
You can move a data chunk to the slower tablespace, but keep the chunk's indexes on the default, faster tablespace:
SELECT move_chunk(chunk => '_timescaledb_internal._hyper_1_4_chunk',destination_tablespace => 'history',index_destination_tablespace => 'pg_default',reorder_index => '_timescaledb_internal._hyper_1_4_chunk_netdata_time_idx');
You can also keep the data in
pg_default but move the index to
Alternatively, you can set up a third tablespace called
and move the data to
history and the indexes to
In Timescale 2.0 and later, you can use
move_chunk with the job scheduler
framework. For more information, see the user-defined actions section.
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