Re: Regression test fails when BLCKSZ is 1kB - Mailing list pgsql-hackers

On Mon, Apr 21, 2008 at 8:20 PM, Tom Lane <tgl@sss.pgh.pa.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