Re: pg_reorg in core?

On 21 September 2012 08:42, Michael Paquier <michael(dot)paquier(at)gmail(dot)com> wrote:
>
>
> On Fri, Sep 21, 2012 at 1:00 PM, Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com>
> wrote:
>>
>> I'm not familiar with pg_reorg, but I wonder why we need a separate
>> program for this task. I know pg_reorg is ok as an external program
>> per se, but if we could optimize CLUSTER (or VACUUM which I'm a little
>> pessimistic about) in the same way, it's much nicer than having
>> additional binary + extension. Isn't it possible to do the same thing
>> above within the CLUSTER command? Maybe CLUSTER .. CONCURRENTLY?
>
> CLUSTER might be more adapted in this case as the purpose is to reorder the
> table.
> The same technique used by pg_reorg (aka table coupled with triggers) could
> lower the lock access of the table.
> Also, it could be possible to control each sub-operation in the same fashion
> way as CREATE INDEX CONCURRENTLY.
> By the way, whatever the operation, VACUUM or CLUSTER used, I got a couple
> of doubts:
> 1) isn't it be too costly for a core operation as pg_reorg really needs many
> temporary objects? Could be possible to reduce the number of objects created
> if added to core though...
> 2) Do you think the current CLUSTER is enough and are there wishes to
> implement such an optimization directly in core?

For me, the Postgres user interface should include
* REINDEX CONCURRENTLY
* CLUSTER CONCURRENTLY
* ALTER TABLE CONCURRENTLY
and also that autovacuum would be expanded to include REINDEX and
CLUSTER, renaming it to automaint.

The actual implementation mechanism for those probably looks something
like pg_reorg, but I don't see it as preferable to include the utility
directly into core, though potentially some of the underlying code
might be.

--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services