Hi Wendell,

an approach to check which is fastest, is the script below (using some appropriate sequence). I can not tell, from the implementation side, which is the one to win, though fn:subsequence() did a good job during the few runs on my machine.

hope this helps, Arve

------ let $seq := (), $cnt := count($seq), $start := random:integer($cnt), $end := random:integer($cnt) return ( (: testing for loop :) prof:dump("for ... "), prof:time( for $x at $p in $seq where $start le $p and $p le $end return $x ),

(: testing subsequence :) prof:dump("fn:subsequence() "), prof:time( fn:subsequence($seq, $start, $end) ),

(: testing subsequence with [...] :) prof:dump("[...]"), prof:time( $seq[$start le position() and position() le $end] ) ) ----

Am 13.08.13 16:58, schrieb Wendell Piez:

Hi,

Currently when I need to batch a database for processing I do something like this:

for $record at $p in $recordSet where ($p ge $start) and ($p ge $end) return $record/process-record(.)

I can imagine why this is more efficient. in BaseX, than using an XPath filter expression, as in

$recordSet[position() ge $start and position() le $end]/process-record(.)

(which is what I might prefer to do in other environments).

But is the 'where' clause the best I can do? XQuery 3.0 has tumbling windows. I am not iterating over subsequences, but rather selecting one (arbitrary) subsequence from a sequence. What's my best approach to this in BaseX?

Thanks, Wendell

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