TAP 1.1, MAXREC and TOP

[Arnold Rots]

Pat got it right :-)

  - Arnold

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Arnold H. Rots                                          Chandra X-ray
Science Center
Smithsonian Astrophysical Observatory                   tel:  +1 617 496
7701
60 Garden Street, MS 67                                      fax:  +1 617
495 7356
Cambridge, MA 02138
arots at cfa.harvard.edu
USA
http://hea-www.harvard.edu/~arots/
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On Mon, Aug 31, 2015 at 3:37 PM, Patrick Dowler <
patrick.dowler at nrc-cnrc.gc.ca> wrote:

> On 31/08/15 02:15 AM, Markus Demleitner wrote:
>
>> Essentially, the question is:  What's to happen when MAXREC=200 is
>> specified in a query parameter, and there's a TOP 4000 clause in
>> QUERY?
>>
>
> Currently: the result must contain up to 200 rows and an overflow
> indicator at the end
> of the table if there are > 200 matching rows. If we said that
> query-specific-limiter
> overrides MAXREC then that behaviour would have to change because overflow
> is
> relative to the effective MAXREC.
>
> The effective MAXREC is what the server decides and they are allowed to
> place such a
> limit. Think of it this way: the query defines a set of rows that the user
> is interested in
> and MAXREC is a negotiation about what will actually be returned. Since
> the service gets
> to decide the limit on return, the query (TOP) can't override effective
> MAXREC so should
> also not override requested MAXREC.
>
> From a client point of view, MAXREC can be used (in addition to TOP) to
> test a query before
> running it (without MAXREC or with a larger value in case the service has
> a small default)... yeah,
> you could just change the TOP value or you could only use MAXREC.
>
> From the point of view of the query capturing the query in the abstract,
> some of those contain
> limits and in that case I favour using TOP to keep the definition of the
> result set in one place.
>
> MAXREC - client-server agreement on size of output, with overflow
> indicator when applicable
> TOP - logical limit on membership in the row set
>
> --
> Patrick Dowler
> Canadian Astronomy Data Centre
> National Research Council Canada
> 5071 West Saanich Road
> Victoria, BC V9E 2E7
>
> 250-363-0044 (office) 250-363-0045 (fax)
>
>
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