What does TOP mean ?

[Douglas Tody]

Yes; basically, TOP is another query parameter, whereas MAXREC controls
the output processing, for any type of service and any query language.


On Tue, 28 Apr 2015, Dave Morris wrote:

>
> On 2015-04-27 16:03, Markus Demleitner wrote:
>> 
>> And regarding Walter's interjection:
>> 
>>> I thought that the difference between MAXREC and TOP is that MAXREC
>>> requires an overflow indicator, while TOP would prohibit it.
>> 
>> Interesting thought -- is it intended to work this way? [it doesn't
>> in DaCHS, and a quick search in the 1.1 specs didn't give me anything
>> pointing in that direction]
>> 
>
> For a TAP service.
>
> I don't know what the specifications say, but as an end user, I would expect 
> that the server returns the lesser of the two, TOP or MAXREC.
>
> However, if MAXREC caused the truncation, then that would be an overflow, if 
> TOP cause the truncation, then it would not.
>
> If TOP > MAXREC, then return MAXREC rows and flag an overflow. Which means 
> this probably would hit MAXREC and return an overflow :
>
>    SELECT TOP 1000000000000000000 * FROM table
>
> If TOP < MAXREC, then return TOP rows and no overflow. So I would not expect 
> to get an overflow for this :
>
>    SELECT TOP 1 * FROM table
>
> I would probably expect the other services to behave in a similar manner.
>
> Hope this helps,
> Dave
>
> --------
> Dave Morris
> Software Developer
> Wide Field Astronomy Unit
> Institute for Astronomy
> University of Edinburgh
> --------
>