[tarantool-patches] Re: [PATCH 3/9] vinyl: use uncompressed run size for range split/coalesce/compaction

Vladimir Davydov vdavydov.dev at gmail.com
Wed Feb 6 13:55:51 MSK 2019

On Wed, Feb 06, 2019 at 01:46:28PM +0300, Konstantin Osipov wrote:
> * Vladimir Davydov <vdavydov.dev at gmail.com> [19/02/06 13:31]:
> > Only because after the patch I don't need to use random() to generate
> > data that would trigger compaction - compaction logic uses uncompressed
> > sizes now so we can use string.rep(), which is faster.
> It is faster but it may impact other properties of the runs - like
> physical run size. For example you begin getting much more pages per
> run, for all runs except the top-level one. 

No. We don't take into account compression when splitting a run in
pages. Never did. Actually, after this patch, it doesn't matter whether
we use data that's easily compressed or not in tests - the result will
be virtually the same.

> I would avoid using string.rep() anywhere in vinyl test data,
> unless I intentionally want to check the effects of inserting data
> with high compression rate.

Okay. I can change that if you wish. Just that there's no difference.

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