Summary:
db_bench's previous default compression level (-1) was not the default compression level in all libraries. In particular, in ZSTD negative values are valid compression levels, while ZSTD's default compression level is three.
This PR changes db_bench's default to be RocksDB's library-independent default compression level (see #3895). I also changed a couple other flags to get their default values from an options object directly rather than hardcoding.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4248
Differential Revision: D9235140
Pulled By: ajkr
fbshipit-source-id: be4e0722d59fa1968832183db36d1d20fcf11e5b
7a9a164276