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Compressed Connections

Turn on protocol compression to reduce the data sent between MariaDB Shell and the server over slow or metered links.

Protocol compression reduces the amount of data that travels between MariaDB Shell and the server, at the cost of CPU time on both ends. It pays off on slow or metered network links, and for large result sets or bulk transfers. On a fast local network, it usually slows things down.

Compression is off by default.

Turning Compression On​

Use -C or --compress on the command line, or the compression connection option in a URI or a dictionary:

mariadb-shell -C dba@db1.example.com/shop --sql

The compression option and --compress accept the following values, in any letter case:

ValueEffect
REQUIRED, true, 1Compression on. -C without a value means REQUIRED.
PREFERREDCompression on.
DISABLED, false, 0Compression off. This is the default.

MariaDB Server compresses the classic protocol with zlib. Connector/C negotiates compression with the server during the handshake, and REQUIRED and PREFERRED behave the same.

To confirm that a session is compressed, check the Compression session status variable:

MariaDB db1.example.com:3306 ssl  SQL > SHOW SESSION STATUS LIKE 'Compression';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Compression   | ON    |
+---------------+-------+

Algorithm and Level Options​

MariaDB Shell also accepts the compression-algorithms and compression-level connection options, which select the algorithm and its level against MySQL 8.0 and later servers. MariaDB Connector/C has no such settings, so with MariaDB Shell these options have no effect:

  • compression-algorithms doesn't select an algorithm, and, unlike in MySQL Shell, it doesn't turn compression on by itself. A connection with only compression-algorithms=zlib is not compressed. Set compression as well.
  • compression-level doesn't change the compression level.

The one check that still applies is a conflict: compression=REQUIRED together with compression-algorithms=uncompressed is rejected.