Fwd: [REVIEW] Re: Compression of full-page-writes

>According to the measurement result, the amount of WAL generated in
>"Multiple Blocks in one run" than that in "Single Block in one run".
>So ISTM that compression of multiple blocks at one run can improve
>the compression ratio. Am I missing something?

Sorry for using unclear terminology. WAL generated here means WAL that gets
generated in each run without compression.
So, the value WAL generated in the above measurement is uncompressed WAL
generated to be specific.
uncompressed WAL = compressed WAL + Bytes saved.

Here, the measurements are done for a constant amount of time rather than
fixed number of transactions. Hence amount of WAL generated does not
correspond to compression ratios of each algo. Hence have calculated bytes
saved in order to get accurate idea of the amount of compression in each
scenario and for various algorithms.

Compression ratio i.e Uncompressed WAL/compressed WAL in each of the above
scenarios are as follows:

Compression algo Multiple Blocks in one run Single Block in one run

LZ4 1.21 1.27

Snappy 1.19 1.25

pglz 1.14 1.16

This shows compression ratios of both the scenarios Multiple blocks and
single block are nearly same for this benchmark.

Thank you,

Rahila Syed