Xquery: Selecting n number of records at a time - xquery

Question

I'm using XQUERY, I have 25000 records saved in Database, I want to select these records in chunks(1000), How do I get the records recursively?

Answer 1

Window queries
You could use the tumbling window for this purpose, sadly it isn't supported by many XQuery engines yet.
For the following suggestions, you have to wrap the results into XML as XQuery only knows flat sequences, no nested ones.
Building your own tumbling windows
You can build your own tumbling windows functions which could look like this one, it creates "window" elements containing $count "item" elements each:
declare function local:window($seq as item()*, $size as xs:integer) as item()* {
for $i in 1 to xs:integer(fn:ceiling(count($seq) div $size))
return
element {"window"} {
for $j in (($i - 1) * $size + 1) to $i*$size
return
element {"item"} {$seq[$j]}
}
};
local:window((2, 4, 6, 8, 10, 12, 14), 3)
Splitting sequences for recursive windows
If you want to solve this problem recursively, you will need some split function which sadly isn't available in standard xquery. You could use $n=1000, work with the "head" elements and call your "worker function" recursively with the "tail".
declare function local:split($seq as item()*, $n as xs:integer) as element()* {
(
element {"head"} {
for $i in subsequence($seq, 1, $n)
return element {"item"} {$i}
},
element {"tail"} {
for $i in subsequence($seq, $n+1)
return element {"item"} {$i}
}
)
};
local:split((2, 4, 6, 8, 10, 12, 14), 3)
To access the tail elements as a sequence, use
local:split((2, 4, 6, 8, 10, 12, 14), 3)[2]//item/data()