Prioritizing queries

[Christopher Petrilli]

Has anyone investigated having either high, or low urgency queries? A
system I'm working on has a constant inflow of data, which has some
queries gainst it which might require long sequential scans. I'm not
that worried about how long those queries take, just that they don't
interfere with other insertions.

This is a bit DSSish, I guess, but I would think it could be managed
by nicing processes?

Chris
--
| Christopher Petrilli
| pe******@gmail. com

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[Steve Atkins]

On Tue, Sep 21, 2004 at 04:24:21PM -0400, Christopher Petrilli wrote:

Has anyone investigated having either high, or low urgency queries? A
system I'm working on has a constant inflow of data, which has some
queries gainst it which might require long sequential scans. I'm not
that worried about how long those queries take, just that they don't
interfere with other insertions.

This is a bit DSSish, I guess, but I would think it could be managed
by nicing processes?

I'd like this feature on some boxes that are being pushed a bit too
close to the limit for comfort.

I've played around with some of the crude ways of doing it. Disk I/O
tends to be the resource that's limited, and process niceness won't
affect that. You'd need to do something like explicitly do a nanosleep
for every X blocks read in by a query or somesuch. Perhaps a
generalization of the vacuum-sleep hack.

Cheers,
Steve

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[Jim C. Nasby]

Some OS's (like FreeBSD) will take process priority into account for
disk I/O. I frankly don't understand why linux doesn't.

On Tue, Sep 21, 2004 at 02:04:26PM -0700, Steve Atkins wrote:

On Tue, Sep 21, 2004 at 04:24:21PM -0400, Christopher Petrilli wrote:

Has anyone investigated having either high, or low urgency queries? A
system I'm working on has a constant inflow of data, which has some
queries gainst it which might require long sequential scans. I'm not
that worried about how long those queries take, just that they don't
interfere with other insertions.

This is a bit DSSish, I guess, but I would think it could be managed
by nicing processes?

I'd like this feature on some boxes that are being pushed a bit too
close to the limit for comfort.

I've played around with some of the crude ways of doing it. Disk I/O
tends to be the resource that's limited, and process niceness won't
affect that. You'd need to do something like explicitly do a nanosleep
for every X blocks read in by a query or somesuch. Perhaps a
generalization of the vacuum-sleep hack.

Cheers,
Steve

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--
Jim C. Nasby, Database Consultant de*****@decibel .org
Give your computer some brain candy! www.distributed.net Team #1828

Windows: "Where do you want to go today?"
Linux: "Where do you want to go tomorrow?"
FreeBSD: "Are you guys coming, or what?"

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