| From: | Julien Rouhaud <julien(dot)rouhaud(at)dalibo(dot)com> |
|---|---|
| To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
| Cc: | James Sewell <james(dot)sewell(at)lisasoft(dot)com>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Paul Ramsey <pramsey(at)cleverelephant(dot)ca>, Andreas Ulbrich <andreas(dot)ulbrich(at)matheversum(dot)de> |
| Subject: | Re: Choosing parallel_degree |
| Date: | 2016-04-06 17:19:06 |
| Message-ID: | 5705450A.80004@dalibo.com |
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| Lists: | pgsql-hackers |
On 06/04/2016 07:38, Amit Kapila wrote:
> On Tue, Apr 5, 2016 at 11:55 PM, Julien Rouhaud
>>
>> In alter_table.sgml, I didn't comment the lock level needed to modify
>> parallel_degree since it requires an access exclusive lock for now.
>> While thinking about it, I think it's safe to use a share update
>> exclusive lock but I may be wrong. What do you think?
>>
>
> We require to keep AccessExclusiveLock for operations which can impact
> Select operation which I think this operation does, so lets
> retain AccessExclusiveLock for now. If somebody else thinks, we should
> not bother about Selects, then we can change it.
>
Ok. Isn't there also some considerations about forcing replanning of
prepared statements using the table for instance?
>>
>> I find your version better once again, but should we keep some
>> consistency between them or it's not important?
>>
>
> I think consistency is good, but this is different from
> max_parallel_degree, so I would prefer to use something on lines of what
> I have mentioned.
>
Agreed, changed in attached v8 (including fix for previous mail).
--
Julien Rouhaud
http://dalibo.com - http://dalibo.org
| Attachment | Content-Type | Size |
|---|---|---|
| rel_parallel_degree_v8.diff | text/plain | 8.1 KB |
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