| From: | Claudio Freire <klaussfreire(at)gmail(dot)com> |
|---|---|
| To: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
| Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Craig Ringer <craig(at)2ndquadrant(dot)com>, Merlin Moncure <mmoncure(at)gmail(dot)com>, David Greco <David_Greco(at)harte-hanks(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Poor performance using CTE |
| Date: | 2012-11-21 16:37:55 |
| Message-ID: | CAGTBQpZCPOpt4azPyUP-Nek94qapYFNfRX-cY=4DD08XM_G2Cw@mail.gmail.com |
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| Lists: | pgsql-performance |
On Wed, Nov 21, 2012 at 1:35 PM, Andrew Dunstan <andrew(at)dunslane(dot)net> wrote:
>>>> Why syntax? What about a guc?
>>>>
>>>> collapse_cte_limit?
>>>
>>> Because there are very good reasons to want to current behaviour. A guc
>>> is a global either/or so I don't see it helping much.
>>
>> set collapse_cte_limit=8;
>> with blah as (blah) select blah;
>>
>> Not global at all.
>>
>
> Then you have to unset it again, which is ugly. You might even want it
> applying to *part* of a query, not the whole thing, so this strikes me as a
> dead end.
Really?
Because I've seen here people that want it generally (because
Oracle/MSSQL/your favourite db does it), and people that don't want it
(generally because they need it). I haven't seen any mention to mixing
fenced and unfenced usage.
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