Decompression

TimescaleDB automatically supports INSERTs into compressed chunks. But if you need to insert a lot of data, for example as part of a bulk backfilling operation, you should first decompress the chunk. Inserting data into a compressed chunk is more computationally expensive than inserting data into an uncompressed chunk. This adds up over a lot of rows.

important

When compressing your data, you can reduce the amount of storage space for your TimescaleDB instance. But you should always leave some additional storage capacity. This gives you the flexibility to decompress chunks when necessary, for actions such as bulk inserts.

This section describes commands to use for decompressing chunks. You can filter by time to select the chunks you want to decompress. To learn how to backfill data, see the backfilling section.

Decompress chunks manually

There are several methods for selecting chunks and decompressing them.

Decompress individual chunks

To decompress a single chunk by name, run this command:

SELECT decompress_chunk('_timescaledb_internal.<chunk_name>');

In this example, chunk_name is the name of the chunk that you want to decompress.

Decompress chunks by time

To decompress a set of chunks based on a time range, you can use the output of show_chunks to decompress each one:

SELECT decompress_chunk(i)
    FROM show_chunks('table_name', older_than, newer_than) i;

Decompress chunks on more precise constraints

If you want to use more precise matching constraints, for example space partitioning, you can construct a command like this:

SELECT tableoid::regclass FROM metrics
  WHERE time = '2000-01-01' AND device_id = 1
  GROUP BY tableoid;
                 tableoid
------------------------------------------
 _timescaledb_internal._hyper_72_37_chunk