Storage and Compression

Viewing Storage and Compression Information

The SHOW DISTRIBUTION statement displays the storage space and compression ratio of a specified time-series database or time-series table.

Note

The compression ratio is a rough calculation and may differ from the actual compression performance. When calculating the compression ratio, the uncompressed data length is calculated based on the column width specified when creating the table. Therefore, for variable-length columns (such as VARCHAR type), if the defined column width is much larger than the actual written data length (for example, defining VARCHAR(1000) but only writing a few characters), the compression ratio will be overestimated.

Privileges

None

Syntax

Parameters

Parameter	Description
db_name	The name of the time-series database to view.
table_name	The name of the time-series table to view. Supports specifying tables in other time-series databases using the db_name.table_name format. When no database is specified, it refers to tables in the current database.

Return Fields

Return fields when viewing a database:

Field	Description
node	Node identifier.
blocks_num	Number of data blocks.
blocks_size	Disk space used.
avg_size	Average data block size.
compression_ratio	Roughly calculated compression ratio.

Return fields when viewing a table:

Field	Description
node_id	Node identifier.
level	Compression level, including last segment (latest segment), entity segment (entity segment), and total (total).
blocks_num	Number of data blocks.
blocks_size	Disk space used.
avg_size	Average data block size.
compression_ratio	Roughly calculated compression ratio.

Examples

• View storage and compression information for a specified database.

  SHOW DISTRIBUTION FROM DATABASE iot;
  

• View storage and compression information for a specified table.

  SHOW DISTRIBUTION FROM TABLE sensors;