reorder_chunk()

Reorder a single chunk's heap to follow the order of an index. This function acts similarly to the PostgreSQL CLUSTER command , however it uses lower lock levels so that, unlike with the CLUSTER command, the chunk and hypertable are able to be read for most of the process. It does use a bit more disk space during the operation.

This command can be particularly useful when data is often queried in an order different from that in which it was originally inserted. For example, data is commonly inserted into a hypertable in loose time order (for example, many devices concurrently sending their current state), but one might typically query the hypertable about a specific device. In such cases, reordering a chunk using an index on (device_id, time) can lead to significant performance improvement for these types of queries.

One can call this function directly on individual chunks of a hypertable, but using add_reorder_policy is often much more convenient.

This function returns void.

SELECT reorder_chunk('_timescaledb_internal._hyper_1_10_chunk', 'conditions_device_id_time_idx');

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runs a reorder on the _timescaledb_internal._hyper_1_10_chunk chunk using the conditions_device_id_time_idx index.