From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
Cc: | Boszormenyi Zoltan <zb(at)cybertec(dot)at>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Michael Meskes <meskes(at)postgresql(dot)org>, Noah Misch <noah(at)leadboat(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, PG Hackers <pgsql-hackers(at)postgresql(dot)org>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Hans-Jürgen Schönig <hs(at)cybertec(dot)at> |
Subject: | Re: Modify the DECLARE CURSOR command tag depending on the scrollable flag |
Date: | 2013-11-27 23:17:16 |
Message-ID: | 9328.1385594236@sss.pgh.pa.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> On 11/27/13, 3:47 PM, Tom Lane wrote:
>> Given these considerations, I think it'd be better to allow explicit
>> application control over whether read-ahead happens for a particular
>> query. And I have no problem whatsoever with requiring that the cursor
>> be explicitly marked SCROLL or NO SCROLL before read-ahead will occur.
> Well, technically, unspecified means NO SCROLL according to the SQL
> standard. A lot of applications in ECPG are ported from other systems,
> which might make that assumption. It wouldn't be very nice to have to
> change all that.
Hm. So you're suggesting that ECPG fix this problem by inserting an
explicit NO SCROLL clause into translated DECLARE CURSOR commands, if
there's not a SCROLL clause?
That would solve the problem of the ECPG library not being sure which
behavior applies, but it might break existing apps that were unknowingly
relying on a simple cursor being scrollable. OTOH any such app would be
subject to breakage anyway as a result of planner changes, so it's hard to
complain against this, as long as it's happening in a major version
update.
I'm for it.
regards, tom lane
From | Date | Subject | |
---|---|---|---|
Next Message | Noah Misch | 2013-11-27 23:18:02 | Re: Incomplete freezing when truncating a relation during vacuum |
Previous Message | Kevin Grittner | 2013-11-27 23:14:11 | Re: MultiXact bugs |