GZIP Function

Overview

The GZIP function performs gzip compression on binary data. It accepts a BINARY type input and returns gzip-compressed BINARY data. It is commonly used to store compressed data in a database to save storage space, or to compress data before transmission to reduce network overhead.

Syntax

gzip(expr)

Parameters

• expr: The input data to be compressed with gzip, of type BINARY.

Returns

Returns a BINARY type value representing the binary data after gzip compression.

Examples

1. Compress a string with gzip (must be cast to BINARY type first):

   SELECT length(gzip(CAST('hello world' AS BINARY))) AS compressed_len; +----------------+ | compressed_len | +----------------+ | 31 | +----------------+

2. Compress with gzip and then decompress with gunzip to verify data integrity (round-trip):

   SELECT CAST(gunzip(gzip(CAST('hello world' AS BINARY))) AS VARCHAR) AS res; +-------------+ | res | +-------------+ | hello world | +-------------+

3. When the input is NULL:

   SELECT gzip(NULL) AS res; +------+ | res | +------+ | NULL | +------+

Notes

• The input parameter must be of BINARY type. To compress string data, first use CAST(expr AS BINARY) for type conversion.
• When the input parameter is NULL, the result is NULL.
• The compressed data is of BINARY type and cannot be used directly as a string.
• Use the gunzip function to decompress gzip-compressed data and restore the original data.
• gzip is a general-purpose lossless compression algorithm; the compression ratio depends on the content and size of the input data.