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chunk_compression_stats.md

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api_name chunk_compression_stats()
excerpt Get compression-related statistics for chunks
topics
compression
keywords
compression
statistics
chunks
information
tags
disk space
schemas
size
api
license type
community
function
products
cloud
mst
self_hosted

import Deprecated2180 from "versionContent/_partials/_deprecated_2_18_0.mdx";

chunk_compression_stats() Community

Superseded by chunk_columnstore_stats(). However, compression APIs are still supported, you do not need to migrate to the hypercore APIs.

Get chunk-specific statistics related to hypertable compression. All sizes are in bytes.

This function shows the compressed size of chunks, computed when the compress_chunk is manually executed, or when a compression policy processes the chunk. An insert into a compressed chunk does not update the compressed sizes. For more information about how to compute chunk sizes, see the chunks_detailed_size section.

Samples

SELECT * FROM chunk_compression_stats('conditions')
  ORDER BY chunk_name LIMIT 2;

-[ RECORD 1 ]------------------+----------------------
chunk_schema                   | _timescaledb_internal
chunk_name                     | _hyper_1_1_chunk
compression_status             | Uncompressed
before_compression_table_bytes |
before_compression_index_bytes |
before_compression_toast_bytes |
before_compression_total_bytes |
after_compression_table_bytes  |
after_compression_index_bytes  |
after_compression_toast_bytes  |
after_compression_total_bytes  |
node_name                      |
-[ RECORD 2 ]------------------+----------------------
chunk_schema                   | _timescaledb_internal
chunk_name                     | _hyper_1_2_chunk
compression_status             | Compressed
before_compression_table_bytes | 8192
before_compression_index_bytes | 32768
before_compression_toast_bytes | 0
before_compression_total_bytes | 40960
after_compression_table_bytes  | 8192
after_compression_index_bytes  | 32768
after_compression_toast_bytes  | 8192
after_compression_total_bytes  | 49152
node_name                      |

Use pg_size_pretty get the output in a more human friendly format.

SELECT pg_size_pretty(after_compression_total_bytes) AS total
  FROM chunk_compression_stats('conditions')
  WHERE compression_status = 'Compressed';

-[ RECORD 1 ]--+------
total | 48 kB

Required arguments

Name Type Description
hypertable REGCLASS Name of the hypertable

Returns

Column Type Description
chunk_schema TEXT Schema name of the chunk
chunk_name TEXT Name of the chunk
compression_status TEXT the current compression status of the chunk
before_compression_table_bytes BIGINT Size of the heap before compression (NULL if currently uncompressed)
before_compression_index_bytes BIGINT Size of all the indexes before compression (NULL if currently uncompressed)
before_compression_toast_bytes BIGINT Size the TOAST table before compression (NULL if currently uncompressed)
before_compression_total_bytes BIGINT Size of the entire chunk table (table+indexes+toast) before compression (NULL if currently uncompressed)
after_compression_table_bytes BIGINT Size of the heap after compression (NULL if currently uncompressed)
after_compression_index_bytes BIGINT Size of all the indexes after compression (NULL if currently uncompressed)
after_compression_toast_bytes BIGINT Size the TOAST table after compression (NULL if currently uncompressed)
after_compression_total_bytes BIGINT Size of the entire chunk table (table+indexes+toast) after compression (NULL if currently uncompressed)
node_name TEXT nodes on which the chunk is located, applicable only to distributed hypertables