maria-developers team mailing list archive

[Eric Bergen <eric.bergen@xxxxxxxxx>]

This looks like a good alternative to the load shedding scripts that a lot
of people run.
On Dec 21, 2011 10:02 AM, "MARK CALLAGHAN" <mdcallag@xxxxxxxxx> wrote:

> A warning would be excellent. An error would be a problem. Returning
> OK is probably not the best result when the examined limit is reached.
>
> On Wed, Dec 21, 2011 at 7:17 AM, Timour Katchaounov
> <timour@xxxxxxxxxxxxxxxx> wrote:
> >>
> >> Hi!
> >>
> >>>>>>> "MARK" == MARK CALLAGHAN<mdcallag@xxxxxxxxx>  writes:
> >>
> >>
> >> MARK>  I want a variant of the LIMIT clause that limits the number of
> rows
> >> MARK>  examined during SELECT processing. This should return OK when the
> >> MARK>  limit is reached -- something like NESTED_LOOP_QUERY_LIMIT. While
> >> MARK>  LIMIT can be LIMIT x and LIMIT x,y. This only supports one
> argument
> >> --
> >> MARK>  LIMIT_ROWS_EXAMINED x. Are you interested in implementing this
> >> feature
> >> MARK>  for me? We will sponsor the work. The purpose of the feature is
> to
> >> MARK>  prevent queries from taking too long when there isn't a great
> index
> >> MARK>  and many rows might be filtered.
> >>
> >> I am a bit afraid of returning 'ok'. Would it not be better to return
> >> an error?
> >>
> >> Another option would be to generate a warning so that the application
> >> can know that they didn't get all rows.
> >
> >
> > This is what I would prefer to do:
> > - process the new LIMIT_ROWS_EXAMINED clause in the same way as LIMIT,
> >  just with a different condition to end query execution,
> > - in addition produce a warning that not all rows were returned.
> >
> > Mark, does the above suit you? If you don't want to check for
> > warnings, you can skip them, however users will have the option
> > to detect that not all rows were returned.
> >
> > Timour
> >
> >>
> >> We can do this and it should be relatively easy to do.
> >>
> >> Regards,
> >> Monty
> >>
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>
>
> --
> Mark Callaghan
> mdcallag@xxxxxxxxx
>
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