| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Mladen Gogala <mladen(dot)gogala(at)vmsinfo(dot)com> |
| Cc: | Dave Crooke <dcrooke(at)gmail(dot)com>, "Plugge, Joe R(dot)" <JRPlugge(at)west(dot)com>, John W Strange <john(dot)w(dot)strange(at)jpmchase(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Index Bloat - how to tell? |
| Date: | 2010-12-18 02:32:48 |
| Message-ID: | AANLkTikedY0=mBZ4nFm3XQK=u08j59yqPMsrsJqA=fgP@mail.gmail.com |
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| Lists: | pgsql-performance |
On Thu, Dec 16, 2010 at 2:27 PM, Mladen Gogala
<mladen(dot)gogala(at)vmsinfo(dot)com> wrote:
> What is "leaf_fragmentation"? How is it defined? I wasn't able to find out
> any definition of that number. How is it calculated. I verified that running
> reindex makes it 0:
Well, according to the code:
/*
* If the next leaf is on an earlier block, it means a
* fragmentation.
*/
if (opaque->btpo_next != P_NONE &&
opaque->btpo_next < blkno)
indexStat.fragments++;
And then the final value is calculated thus:
snprintf(values[j++], 32, "%.2f", (double)
indexStat.fragments / (double) indexStat.leaf_pages * 100.0);
This doesn't really match my definition of the word "fragmentation", though...
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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