Compression policy

You can enable compression on individual hypertables, by declaring which column you want to segment by.

Enable a compression policy

This page uses an example table, called example, and segments it by the device_id column. Every chunk that is more than seven days old is then marked to be automatically compressed. The source data is organized like this:

time	device_id	cpu	disk_io	energy_consumption
8/22/2019 0:00	1	88.2	20	0.8
8/22/2019 0:05	2	300.5	30	0.9

Enabling compression

At the psql prompt, alter the table:


ALTER TABLE example SET (
  timescaledb.compress,
  timescaledb.compress_segmentby = 'device_id'
);

Add a compression policy to compress chunks that are older than seven days:
```
SELECT add_compression_policy('example', INTERVAL '7 days');
```

For more information, see the API reference for ALTER TABLE (compression) and add_compression_policy.

View current compression policy

To view the compression policy that you've set:


SELECT * FROM timescaledb_information.jobs
  WHERE proc_name='policy_compression';

For more information, see the API reference for timescaledb_information.jobs.

Pause compression policy

To disable a compression policy temporarily, find the corresponding job ID and then call alter_job to pause it:


SELECT * FROM timescaledb_information.jobs where proc_name = 'policy_compression' AND relname = 'example'


SELECT alter_job(<job_id>, scheduled => false);

To enable it again:


SELECT alter_job(<job_id>, scheduled => true);

Remove compression policy

To remove a compression policy, use remove_compression_policy:


SELECT remove_compression_policy('example');

For more information, see the API reference for remove_compression_policy.

Disable compression

You can disable compression entirely on individual hypertables. This command works only if you don't currently have any compressed chunks:


ALTER TABLE <EXAMPLE> SET (timescaledb.compress=false);

If your hypertable contains compressed chunks, you need to decompress each chunk individually before you can turn off compression.