hypertable_columnstore_stats()

Since 2.18.0

Note

hypertable_columnstore_stats() replaces hypertable_compression_stats(), deprecated in 2.18.0. The parameters are the same.

Retrieve compression statistics for the columnstore.

For more information about using hypertables, including chunk size partitioning, see hypertables.

Samples

To retrieve compression statistics:

• Show the compression status of the conditions hypertable:

  SELECT * FROM hypertable_columnstore_stats('conditions');

  Returns:

  -[ RECORD 1 ]------------------+------
  total_chunks                   | 4
  number_compressed_chunks       | 1
  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 hypertable_columnstore_stats('conditions');

  Returns:

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

Arguments

The syntax is:

SELECT * FROM hypertable_columnstore_stats('<hypertable_name>');

Name	Type	Description
hypertable	REGCLASS	hypertable to show statistics for

Returns

Column	Type	Description
total_chunks	BIGINT	The number of chunks used by the hypertable. Returns NULL if compression_status == Uncompressed.
number_compressed_chunks	BIGINT	The number of chunks used by the hypertable that are currently compressed. Returns NULL if compression_status == Uncompressed.
before_compression_table_bytes	BIGINT	Size of the heap before compression. Returns NULL if compression_status == Uncompressed.
before_compression_index_bytes	BIGINT	Size of all the indexes before compression. Returns NULL if compression_status == Uncompressed.
before_compression_toast_bytes	BIGINT	Size the TOAST table before compression. Returns NULL if compression_status == Uncompressed.
before_compression_total_bytes	BIGINT	Size of the entire table (before_compression_table_bytes + before_compression_index_bytes + before_compression_toast_bytes) before compression. Returns NULL if compression_status == Uncompressed.
after_compression_table_bytes	BIGINT	Size of the heap after compression. Returns NULL if compression_status == Uncompressed.
after_compression_index_bytes	BIGINT	Size of all the indexes after compression. Returns NULL if compression_status == Uncompressed.
after_compression_toast_bytes	BIGINT	Size the TOAST table after compression. Returns NULL if compression_status == Uncompressed.
after_compression_total_bytes	BIGINT	Size of the entire table (after_compression_table_bytes + after_compression_index_bytes + after_compression_toast_bytes) after compression. Returns NULL if compression_status == Uncompressed.
node_name	NAME	nodes on which the hypertable is located, applicable only to distributed hypertables. Returns NULL if compression_status == Uncompressed.