Re: "set nice" running a transaction in a lower priority?

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Re: "set nice" running a transaction in a lower priority?

От:
Tom Lane <tgl@sss.pgh.pa.us>
Дата:
Richard Huxton  writes:
> On Wednesday 12 Jun 2002 6:33 pm, Clark C . Evans wrote:
>> I was wondering if there is a way to set transaction
>> priority so that it takes its good sweet time and
>> handles other queries quickly?

> Not really - and it might be counter-productive to slow down the import. If 
> another transaction can't complete until the import is finished then 
> everything could end up delayed.

> I guess you could nice the pid of the relevant backend process,

That would be a bad idea for the same reason --- you'd get into
priority-inversion scenarios where foreground processes are waiting for
the low-priority process, which can't run because other foreground
processes are hogging all the CPU.

> but I'd be 
> inclined to batch the import into sections of 5000 records or so and sleep 
> for a second between batches.

Some kind of throttle on the client side seems like a better idea to me
too.

			regards, tom lane

"set nice" running a transaction in a lower priority?

От:
"Clark C . Evans" <cce@clarkevans.com>
Дата:
I was wondering if there is a way to set transaction
priority so that it takes its good sweet time and
handles other queries quickly?  I have an "import"
process that takes a while, and I don't mind having
the user who is doing the import wait; but it would
be nice to have the box more responsive while the 
import is occuring.

Best,

Clark

Re: "set nice" running a transaction in a lower priority?

От:
"Clark C . Evans" <cce@clarkevans.com>
Дата:
On Thu, Jun 13, 2002 at 09:09:46AM -0400, Tom Lane wrote:
| Some kind of throttle on the client side seems like a better idea

Thanks.  This is exactly what is needed.  

;) Clark

Re: "set nice" running a transaction in a lower priority?

От:
Richard Huxton <dev@archonet.com>
Дата:
On Wednesday 12 Jun 2002 6:33 pm, Clark C . Evans wrote:
> I was wondering if there is a way to set transaction
> priority so that it takes its good sweet time and
> handles other queries quickly?

Not really - and it might be counter-productive to slow down the import. If 
another transaction can't complete until the import is finished then 
everything could end up delayed.

I guess you could nice the pid of the relevant backend process, but I'd be 
inclined to batch the import into sections of 5000 records or so and sleep 
for a second between batches.

- Richard Huxton

Re: "set nice" running a transaction in a lower

От:
Doug Fields <dfields-pg-general@pexicom.com>
Дата:
On a related topic:

Is it possible to run a background query (I use JDBC)?

For example, I would like to run a query which I know takes a long time to 
process, without holding the connection open and/or synchronously waiting 
for the query response.

This is related to the "import" because I typically do my import to a temp 
table, then INSERT...SELECT into the real table which is very slow because 
of all the indexes which have to be handled.

Thanks,

Doug
FAQ