Dropping chunks manually

As an example, if you have a hypertable definition of conditions where you collect raw data into chunks of one day:

CREATE TABLE conditions(
    time TIMESTAMPTZ NOT NULL,
    device INTEGER,
    temperature FLOAT
);
SELECT * FROM create_hypertable('conditions', 'time',
       chunk_time_interval => INTERVAL '1 day');

If you collect a lot of data and realize that you never actually use raw data older than 30 days, you might want to delete data older than 30 days from conditions.

However, deleting large swaths of data from tables can be costly and slow if done row-by-row using the standard DELETE command. Instead, TimescaleDB provides a function drop_chunks that quickly drop data at the granularity of chunks without incurring the same overhead.

For example:

SELECT drop_chunks('conditions', INTERVAL '24 hours');

This will drop all chunks from the hypertable conditions that only include data older than this duration, and will not delete any individual rows of data in chunks.

For example, if one chunk has data more than 36 hours old, a second chunk has data between 12 and 36 hours old, and a third chunk has the most recent 12 hours of data, only the first chunk is dropped when executing drop_chunks. Thus, in this scenario, the conditions hypertable will still have data stretching back 36 hours.

For more information on the drop_chunks function and related parameters, please review the [API documentation][drop_chunks].