| From: | "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com> |
|---|---|
| To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | "Peter Eisentraut" <peter_e(at)gmx(dot)net>, pgsql-hackers(at)postgresql(dot)org, "Zdenek Kotala" <Zdenek(dot)Kotala(at)sun(dot)com> |
| Subject: | Re: Regression test fails when BLCKSZ is 1kB |
| Date: | 2008-04-21 17:24:49 |
| Message-ID: | 2e78013d0804211024g2e3fae9cw3790756fa4206274@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Apr 21, 2008 at 8:20 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> No, the reason you don't see that is that plain VACUUM doesn't move
> tuples around.
>
I know. But plain VACUUM can free up dead space which can be used for
subsequent updates/inserts and that can cause reordering. For example:
Case 1.
Insert 100 records --- goes into block 1 .. 10
Delete 100 records
Insert 100 more records --- goes into 11 .. 20
Case 2.
Insert 100 records --- goes into block 1 .. 10
Delete 100 records
*Autovacuum triggers*
Insert 100 more records -- goes into block 1 .. 10
Thanks,
Pavan
--
Pavan Deolasee
EnterpriseDB http://www.enterprisedb.com
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