Comment 13 for bug 1269547

Tom and others -

I have pushed lp:~laurynas-biveinis/percona-server/sparse-bitmap-prototype for estimating space saving with a sparse bitmap representation.

The branch has one new option, --innodb-sparse-changed-page-bitmap=TRUE|FALSE, dynamic, disabled by default, that writes compact bitmap pages if considered profitable at each checkpoint. The resulting bitmap files are NOT usable, the branch itself is strictly for experimental purposes.

For both option values it will print a sparsity measure to stderr, and if the option is enabled, it will also print how many bytes were actually written and how many bytes were written if the default representation were used instead.

Tested very lightly. I have worked out what I believe is the correct cutoff value between representations, but feel free to tweak it in the code if you find that sparse bitmap takes more bytes than a dense one.

Thanks in advance for any space saving measurements and any other feedback.