Contents

• PostgreSQL GZIP/GUNZIP Functions
  • Motivation
  • Examples
  • Functions
  • Installation
    • UNIX

PostgreSQL GZIP/GUNZIP Functions

Motivation

Sometimes you just need to compress your bytea object before you return it to the client.

Sometimes you receive a compressed binary object from the client, and you have to uncompress it to do something useful.

This extension is for that.

Examples

> SELECT gzip('this is my this is my this is my this is my text');

                                   gzip
--------------------------------------------------------------------------
 \x1f8b08000000000000132bc9c82c5600a2dc4a851282ccd48a12002e7a22ff30000000

What, the compressed output is longer?!? No, it only looks that way, because in hex every character requires two hex digits. The original string looks like this in hex:

> SELECT 'this is my this is my this is my this is my text'::bytea;

                                               bytea
----------------------------------------------------------------------------------------------------
 \x74686973206973206d792074686973206973206d792074686973206973206d792074686973206973206d792074657874

And for really long, repetitive things, compression naturally works like a charm:

> SELECT gzip(repeat('this is my ', 100));

                                               bytea
----------------------------------------------------------------------------------------------------
 \x1f8b08000000000000132bc9c82c5600a2dc4a859251e628739439ca24970900d1341c5c4c040000

Converting a bytea back into an equivalent text uses the encode() function with the escape encoding.

> SELECT encode(gunzip(gzip('this is my this is my this is my this is my text')), 'escape')

                      encode
--------------------------------------------------
 this is my this is my this is my this is my text

Functions

• gzip(uncompressed BYTEA, [compression_level INTEGER]) returns BYTEA
• gzip(uncompressed TEXT, [compression_level INTEGER]) returns BYTEA
• gunzip(compressed BYTEA) returns BYTEA

Installation

UNIX

If you have PostgreSQL devel packages and zlib installed, you should have pg_config on your path, so you should be able to just run make, then make install, then in your database CREATE EXTENSION gzip.

If your libz is installed in a non-standard location, you may need to edit ZLIB_PATH in the Makefile.