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Re: 8.3.0 Core with concurrent vacuum fulls

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com>
Cc: "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com>, "Gavin M(dot) Roy" <gmr(at)myyearbook(dot)com>, "Alvaro Herrera" <alvherre(at)commandprompt(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: 8.3.0 Core with concurrent vacuum fulls
Date: 2008-03-06 18:00:25
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
"Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com> writes:
> On Wed, Mar 5, 2008 at 9:29 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> [ thinks some more... ]  I guess we could use a flag array dimensioned
>> MaxHeapTuplesPerPage to mark already-processed tuples, so that you
>> wouldn't need to search the existing arrays but just index into the flag
>> array with the tuple's offsetnumber.

> We can actually combine this and the page copying ideas. Instead of copying
> the entire page, we can just copy the line pointers array and work on the copy.

I think that just makes things more complex and fragile.  I like
Heikki's idea, in part because it makes the normal path and the WAL
recovery path guaranteed to work alike.  I'll attach my work-in-progress
patch for this --- it doesn't do anything about the invalidation
semantics problem but it does fix the critical-section-too-big problem.

			regards, tom lane

Attachment: heap_prune_refactor.patch.gz
Description: application/octet-stream (6.5 KB)

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