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The legacy compression parameters interact with the newer parameters and their semantics change as follows: 

•The meaning of the legacy --compress  option depends on whether --compression-algorithms  is specified: 

•When --compression-algorithms  is not specified, --compress  is equivalent to specifying a client-side algorithm set of zlib,uncompressed . 

•When --compression-algorithms  is specified, --compress  is equivalent to specifying an algorithm set of zlib  and the full client-side algorithm set is the union of zlib  plus the algorithms specified by --compression-algorithms . For example, with both -- compress  and --compression-algorithms=zlib,zstd , the permitted-algorithm set is zlib  plus zlib,zstd ; that is, zlib,zstd . With both --compress  and -- compression-algorithms=zstd,uncompressed , the permitted-algorithm set is zlib  plus zstd,uncompressed ; that is, zlib,zstd,uncompressed . 

•The same type of interaction occurs between the legacy MYSQL_OPT_COMPRESS  option and the MYSQL_OPT_COMPRESSION_ALGORITHMS  option for the mysql_options() C API function. 

•If the slave_compressed_protocol  system variable is enabled, it takes precedence over MASTER_COMPRESSION_ALGORITHMS  and connections to the source use zlib  compression if both source and replica permit that algorithm. If slave_compressed_protocol  is disabled, the value of MASTER_COMPRESSION_ALGORITHMS  applies. 

## Monitoring Connection Compression 

<img src='content_image/777514.jpg'>

## Note 

The legacy compression-control parameters are deprecated as of MySQL 8.0.18; expect it to be removed in a future version of MySQL. 

The Compression  status variable is ON  or OFF  to indicate whether the current connection uses compression. 

The mysql  client \status  command displays a line that says Protocol: Compressed  if compression is enabled for the current connection. If that line is not present, the connection is uncompressed. 

As of 8.0.14, the MySQL Shell \status  command displays a Compression:  line that says Disabled  or Enabled  to indicate whether the connection is compressed. 

As of MySQL 8.0.18, these additional sources of information are available for monitoring connection compression: 

•To monitor compression in use for client connections, use the Compression_algorithm  and Compression_level  status variables. For the current connection, their values indicate the compression algorithm and compression level, respectively. 

•To determine which compression algorithms the server is configured to permit for incoming connections, check the protocol_compression_algorithms  system variable. 

•For source/replica replication connections, the configured compression algorithms and compression level are available from multiple sources: 

•The Performance Schema replication_connection_configuration  table has COMPRESSION_ALGORITHMS  and ZSTD_COMPRESSION_LEVEL  columns. 

