Re: [HACKERS] union and LIMIT problem - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: [HACKERS] union and LIMIT problem
Date
Msg-id 199910071739.NAA02643@candle.pha.pa.us
Whole thread Raw
In response to Re: [HACKERS] union and LIMIT problem  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
> >>>> * UNION with LIMIT fails
> >> 
> >> and must fail by it's implementation. LIMIT is handled by the
> >> outermost executor loop, suppressing OFFSET result tuples and
> >> stopping execution after LIMIT results sent to the client.
> 
> > Ah, but it works sometimes:
> 
> Well, the real question is what do you mean by "works" or "fails".
> In particular, do you think that LIMIT applies to the overall result
> of the whole query, or to any one sub-select?

Should apply to overall result, like ORDER BY.

> 
> IIRC, ORDER BY is supposed to apply to the end result (and you can
> only write it at the very end of the query, not after a sub-select),
> and I'd vote for making LIMIT work the same.  In which case the
> executor should be fine, and we probably just have a problem with
> the parser hanging the info on the wrong node of the querytree...
> 
>             regards, tom lane
> 


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