pgzstd
Introduction
pgzstd is a PostgreSQL extension that provides functions for compressing and uncompressing Zstandard frames, with support for custom dictionaries.
Prerequisites
- PostgreSQL headers, libraries and PGXS build infrastructure
pg_configmust be in yourPATH- Zstandard
Building
Run make to build the extension.
Installation
Run make install as root (e.g. with sudo) to install the extension.
Debian package
The repository also contains the files for building a Debian package, which can
be done by running pg_buildext updatecontrol followed by dpkg-buildpackage.
I distribute pre-built versions for stable amd64 Debian using the
apt.postgresql.org repository in my personal APT repository. Run
apt-get install postgresql-PGVERSION-zstd as root after setting up the
repository.
Usage
Run CREATE EXTENSION zstd to install the extension in the current database.
Three functions are provided:
| Function | Return Type |
|---|---|
zstd_compress(data bytea [, dictionary bytea [, level integer ]]) |
bytea |
zstd_decompress(data bytea [, dictionary bytea ]) |
bytea |
zstd_length(data bytea) |
integer |
zstd_compress compresses the provided data and returns a Zstandard frame. A
preset dictionary may also be provided. The default compression level may
also be overriden, valid values range from 1 (best speed) to 22 (best
compression). The default level is 3.
If you want to override the compression level without using a dictionary, set
dictionary to NULL.
zstd_decompress decompresses the provided Zstandard frame in data and
returns the uncompressed data. A preset dictionary, matching the dictionary
used to compress the data, may also be provided.
zstd_length returns the decompressed length of the provided Zstandard frame.
If ZSTD_getFrameContentSize() is available it returns NULL if the length is
unknown. If unavailable, it isn't possible to distinguish the error, unknown
decompressed length and zero decompressed length cases.
Example
gpe=# CREATE EXTENSION zstd;
CREATE EXTENSION
gpe=# SELECT zstd_compress('hello hello hello hello', 'hello hello', 3);
zstd_compress
--------------------------------------
\x28b52ffd2017450000000200291c6c1420
(1 row)
gpe=# SELECT convert_from(zstd_decompress('\x28b52ffd2017450000000200291c6c1420', 'hello hello'), 'utf-8');
convert_from
-------------------------
hello hello hello hello
(1 row)
gpe=# SELECT zstd_length('\x28b52ffd2017450000000200291c6c1420');
zstd_length
-------------
23
(1 row)
gpe=#
License
This project is available under the terms of the ISC license, which is similar
to the 2-clause BSD license. See the LICENSE file for the copyright
information and licensing terms.