The function my_compress (in mysys/my_compress.c) uses the default level
of zlib compression when compressing network packets. For my
unscientific sample data 'gzip -1' is 2.5 to 3X faster than 'gzip' (the
default level of compression made the result file 25% smaller than the
fastest level). With a mysqld compiled to use the fastest level of zlib
compression, fetches of large amounts of data were faster when using the
fastest level of zlib compression rather than the default. These
results held even when the client and server were reasonably far apart
(ping time is 60ms).

My belief is that compression of network packets is more likely to be
useful when the fastest level of zlib compression is used. Of course,
MySql clients with really high latency connections to servers or uses
where network traffic is significantly more expensive than server CPU
time may disagree.

Are there clients that benefit from using the default level of zlib
compression?

--
Mark Callaghan
mcallaghan (AT) google (DOT) com

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