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Version: Candidate-4.0

column_size & column_compressed_size

These functions return the size information of table columns for storage analysis and optimization. Both functions work with the [_META_] hint to inspect segment file metadata.

column_size​

Returns the decompressed size of a column in bytes.

Syntax​

-- Do not omit the brackets [] in the hint.
SELECT column_size(column_name) FROM table_name [_META_];

Parameters​

  • column_name: The name of the column for which you want to get the decompressed size.

Return value​

Returns the decompressed size of the column in bytes as a BIGINT value.

column_compressed_size​

Returns the compressed size of a column in bytes.

Syntax​

-- Do not omit the brackets [] in the hint.
SELECT column_compressed_size(column_name) FROM table_name [_META_];

Parameters​

  • column_name: The name of the column for which you want to get the compressed size.

Return value​

Returns the compressed size of the column in bytes as a BIGINT value.

Usage notes​

  • Both functions must be used with the [_META_] hint to access metadata information.
  • The functions scan the metadata of underlying segment files using the META_SCAN operator.
  • For complex data types (JSON, ARRAY, MAP, STRUCT), the functions recursively calculate the size of all sub-columns.
  • column_size returns the uncompressed column size.
  • column_compressed_size returns the compressed on-disk size.

Examples​

-- Get both decompressed and compressed sizes of columns
SELECT 
    column_size(name) as name_decompressed_size,
    column_compressed_size(name) as name_compressed_size,
    column_size(description) as desc_decompressed_size,
    column_compressed_size(description) as desc_compressed_size
FROM products [_META_];