| From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
|---|---|
| To: | Mark Kirkwood <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz> |
| Cc: | kskim(at)bitnine(dot)net, Lukas Fittl <lukas(at)fittl(dot)com>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Btree Index on PostgreSQL and Wiredtiger (MongoDB3.2) |
| Date: | 2016-08-12 17:44:53 |
| Message-ID: | CAMkU=1w0BHPgJ65uZ=TBGkUJ=h-61vEcyLN3Etk6qJKEiEWaGQ@mail.gmail.com |
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On Fri, Aug 12, 2016 at 1:40 AM, Mark Kirkwood
<mark(dot)kirkwood(at)catalyst(dot)net(dot)nz> wrote:
> After examining the benchmark design - I see we are probably not being
> helped by the repeated insertion of keys all of form 'userxxxxxxx' leading
> to some page splitting.
But shouldn't that still leave us with a 75% full index, rather than
slightly over 50% full?
The leaf pages start at 50%, grow to 100%, then split back to 50%,
then grow back to 100%. So the average should be about 75%.
> However your index rebuild gets you from 5 to 3 GB - does that really help
> performance significantly?
It can make a big difference, depending on how much RAM you have.
Cheers,
Jeff
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