Re: pg_reorg in core?

2012/09/25 0:15, Simon Riggs wrote:
> On 21 September 2012 08:42, Michael Paquier <michael.paquier@gmail.com> wrote:
>>
>>
>> On Fri, Sep 21, 2012 at 1:00 PM, Hitoshi Harada <umi.tanuki@gmail.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.

I think it depends on what trade-off we can see.

AFAIK, basically, rebuilding tables and/or indexes has
a trade-off between "lock-free" and "disk-space".

So, if we have enough disk space to build a "temporary"
table/index when rebuilding a table/index, "concurrently"
would be a great option, and I would love it to have
in core.

Regards,
-- 
Satoshi Nagayasu <snaga@uptime.jp>
Uptime Technologies, LLC. http://www.uptime.jp