Re: heap_page_prune comments - Mailing list pgsql-hackers

From Robert Haas
Subject Re: heap_page_prune comments
Date
Msg-id CA+TgmoYLBcUgqqdE=sMKwcf5ZCsSsrcPGO8fpjGBKv_TPKdv6w@mail.gmail.com
Whole thread Raw
In response to Re: heap_page_prune comments  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: heap_page_prune comments
List pgsql-hackers
On Fri, Nov 4, 2011 at 10:46 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> Seems a little hackish, though: we'd be reporting an amount of
>> freespace that we've deliberately set to an incorrect value.  I'm
>> almost thinking we should report the freespace that's actually
>> available, on the theory that Bload Is Bad (TM).
>
> IIRC, this code is following the very longstanding precedent of
> RelationGetBufferForTuple.

I don't understand the analogy - that function isn't freeing any
space, just searching for a block that already has some.  And it does
update the free space map if the free space map is found to be out of
date, whereas this function does not.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


pgsql-hackers by date:

Previous
From: Tom Lane
Date:
Subject: Re: Show statistics target in \d+
Next
From: Marti Raudsepp
Date:
Subject: Re: IDLE in transaction introspection