MarkLogic 10 Product Documentationxdmp:set
xdmp:set( $variable as item()*, $expr as item()* ) as empty-sequence()
Summary
Set the value of a variable to the specified expression. The
xdmp:set command allows you to introduce changes to the
state (side effects) of a query by changing the value of a variable to
something other than what it is bound to.
| Parameters | |
|---|---|
| variable | A variable to set. |
| expr | A value to set the variable. |
Usage Notes
When a variable is bound to a sequence in afor loop, and when
that variable is changed by xdmp:set in the return
clause, the change only affects the value for one iteration of the
for loop at a time; when the next value is sent to the return
clause, it is set to the next value in the sequence specified in the
for clause. The value changes only after the
xdmp:set call is made.
Example
(: set the value of the variable $x to 1234 and then print out $x :) let $x := 12 return (xdmp:set($x, 1234), $x) => 1234
Example
(: set the value of the variable $x to 5 and then print out $x for each value of $y :) for $x in (1, 2) for $y in ($x, $x) return ($y, xdmp:set($x, 5), $x) => (1, 5, 1, 5, 2, 5, 2, 5)
Example
(: note the effect on $z of changing the
value of $x :)
for $x in (1, 2)
for $y in (3,4)
for $z in ($x, $x)
return
($z, xdmp:set($x, 5))
=> (1, 1, 5, 5, 2, 2, 5, 5)
Example
(: every time the name of the input node changes, output the new name :) let $n := () for $i in (<x>1</x>, <x>2</x>, <y>3</y>) return ( if (name($i) eq $n) then () else (xdmp:set($n, name($i)), $n) , data($i) ) => (x, 1, 2, y, 3)