| From: | Alexander Korotkov <aekorotkov(at)gmail(dot)com> |
|---|---|
| To: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
| Cc: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Fillfactor for GIN indexes |
| Date: | 2015-07-21 13:14:25 |
| Message-ID: | CAPpHfdvpzBFs5=93USnjvMaLE8VXOTk5r2Sr+X3z9M03xD9Fng@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Jul 21, 2015 at 3:52 PM, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
> On 07/21/2015 02:56 PM, Alexander Korotkov wrote:
>
>> Probably, but currently we are in quite unlogical situation. We have
>> default fillfactor = 90 for GiST where it has no use cases at all and
>> effectively is just a waste of space.
>>
>
> Why is it useless for GiST?
It's because all of GiST pages are produced by page splits. So, just after
CREATE INDEX GiST pages aren't tightly packed in average. Actually, they
could be tightly packed by incredible coincidence, but for large indexes
it's quite safe assumption that they are not. With GiST we don't have storm
of page splits after index creation with fillfactor = 100. So, why should
we reserve additional space with fillfactor = 90?
------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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