The CQL 3.1 documentation specifies that for disabling compression,
users should use an empty string:
ALTER TABLE mytable WITH COMPRESSION = {'sstable_compression': ''};
However, Cassandra also accepts the absence of the sstable_compression
option to disable compression. The patch 7c28ed prevented this behavior
in Scylla, which this patch aims to fix.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Message-Id: <1478639499-4183-1-git-send-email-duarte@scylladb.com>
This patch extracts the definition of the default compressor into the
compression_parameters class, so that the table and view creation
statements don't have to explicitly deal with it.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Following Cassandra, our default sstable compression chunk size is 64 KB.
The big downside of this default size is that small reads need to read
and uncompress a large chunk, around 32 KB (if compression halves the data
size). In this patch we switch the default chunk size to 4 KB, which allows
faster small reads (the report in issue #1337 was of a 60-fold speedup...).
Since commit 2f56577, large reads will not be signficantly slowed down by
changing to a small chunk size. The remaining potential downside of this
change is lowering of the compression ratio because of the smaller chunks
individually compressed. However, experimentation shows that the compression
ratio is hurt somewhat, but not dramatically, by lowering the chunk size:
A recent survey of Cassandra compression in
https://www.percona.com/blog/2016/03/09/evaluating-database-compression-methods/
reports a compression ratio of 2 for 64 KB chunks, vs. 1.75 for 4 KB chunks.
My own test on a cassandra-stress workload (whose data is relatively hard
to compress), showed compression ratio 1.25 for 64 KB chunk, vs. 1.23 for
4 KB chunks.
Also remember that if a user wants to control the chunk length for a
particular table, he can - the 64 KB or 4 KB sizes are just the default.
Fixes#1337
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <1467063335-12096-1-git-send-email-nyh@scylladb.com>
Passing a single enum specifying a compressor type around is not enough,
since there are other compression options user may want to specify.
Signed-off-by: Paweł Dziepak <pdziepak@cloudius-systems.com>
The field compressor is about saying which compressor algorithm
must be used in compression of sstable data file.
This is a small step towards compressed sstable data file.
Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
