GUNZIP Function

Overview

The GUNZIP function decompresses gzip-compressed binary data. It accepts a BINARY type input (must be valid gzip-compressed data) and returns the decompressed BINARY data. It is commonly used to restore data compressed by the gzip function, or to decompress externally provided gzip-format data.

Syntax

gunzip(expr)

Parameters

• expr: The input data to be decompressed with gzip, of type BINARY. The data must be in valid gzip-compressed format.

Returns

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

Examples

1. 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 | +-------------+

2. Decompress compressed data and check the length:

   SELECT length(gunzip(gzip(CAST('hello world' AS BINARY)))) AS decompressed_len; +------------------+ | decompressed_len | +------------------+ | 11 | +------------------+

3. When the input is NULL:

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

Notes

• The input parameter must be of BINARY type and must be valid gzip-compressed data. If the input data is not in valid gzip format, an error will be returned.
• When the input parameter is NULL, the result is NULL.
• The decompressed data is of BINARY type. To use it as a string, use CAST(expr AS VARCHAR) for type conversion.
• Use the gzip function to compress data, and pair it with gunzip for data compression and decompression.
• gunzip is the inverse of gzip: gunzip(gzip(data)) returns the original data.