Hi with the factbook.xml database open in the 7.0.2 gui declare function local:linkto($id as xs:string){ let $d:=//city let $a:=$d[@id=$id] return $a }; local:linkto("f0_1461") Gives the "no context item for root" error on the //city line, but declare function local:linkto($id as xs:string){ let $a:=//city[@id=$id] return $a }; local:linkto("f0_1461") Works fine. Should it give the same error? If it should, and I try to pass the nodes into the function then the relative performance is not good at all. declare function local:linkto2($id as xs:string,$nodes as node()*){ let $c:=$nodes[@id=$id] let $n:=name($c[1]) return <a href="/fb/{$n}/{$id}"> {$c/name/string()} </a> }; let $caps:=//country/@capital/string() for $id in $caps return local:linkto2($id,//city) /Andy
Hi Andy, yes, it should give the same error. I only have tried the latest 7.1 snapshot, which returns errors for both of the queries. The performance may be suboptimal here, as the equality predicate in the function cannot be optimized for index access (this is because the incoming nodes may relate to a database instance that has no attribute index). This may be changed in future by choosing the best evaluation plan at runtime. Hope this helps, Christian On Sat, Dec 10, 2011 at 11:55 PM, Andy Bunce <bunce.andy@gmail.com> wrote:
Hi with the factbook.xml database open in the 7.0.2 gui
declare function local:linkto($id as xs:string){ let $d:=//city let $a:=$d[@id=$id] return $a }; local:linkto("f0_1461")
Gives the "no context item for root" error on the //city line, but
declare function local:linkto($id as xs:string){ let $a:=//city[@id=$id] return $a }; local:linkto("f0_1461")
Works fine. Should it give the same error? If it should, and I try to pass the nodes into the function then the relative performance is not good at all. declare function local:linkto2($id as xs:string,$nodes as node()*){ let $c:=$nodes[@id=$id] let $n:=name($c[1]) return <a href="/fb/{$n}/{$id}"> {$c/name/string()} </a> };
let $caps:=//country/@capital/string() for $id in $caps return local:linkto2($id,//city)
/Andy
Hi Christian, Thanks for the explanation. So functions never use indices are the moment? /Andy On Sat, Dec 10, 2011 at 11:02 PM, Christian Grün <christian.gruen@gmail.com>wrote:
Hi Andy,
yes, it should give the same error. I only have tried the latest 7.1 snapshot, which returns errors for both of the queries. The performance may be suboptimal here, as the equality predicate in the function cannot be optimized for index access (this is because the incoming nodes may relate to a database instance that has no attribute index). This may be changed in future by choosing the best evaluation plan at runtime.
Hope this helps, Christian
On Sat, Dec 10, 2011 at 11:55 PM, Andy Bunce <bunce.andy@gmail.com> wrote:
Hi with the factbook.xml database open in the 7.0.2 gui
declare function local:linkto($id as xs:string){ let $d:=//city let $a:=$d[@id=$id] return $a }; local:linkto("f0_1461")
Gives the "no context item for root" error on the //city line, but
declare function local:linkto($id as xs:string){ let $a:=//city[@id=$id] return $a }; local:linkto("f0_1461")
Works fine. Should it give the same error? If it should, and I try to pass the nodes into the function then the relative performance is not good at all. declare function local:linkto2($id as xs:string,$nodes as node()*){ let $c:=$nodes[@id=$id] let $n:=name($c[1]) return <a href="/fb/{$n}/{$id}"> {$c/name/string()} </a> };
let $caps:=//country/@capital/string() for $id in $caps return local:linkto2($id,//city)
/Andy
Thanks for the explanation. So functions never use indices are the moment?
..unless the documents/database are specified within the function. For example, the following function will indeed be optimized, if the 'DB' database provides a text index: declare function($key as xs:string) { db:open('DB')//*[text() = $key] }; However, you can explicitly take advantage of a text index by using the db:text() function: declare function($db, $key) { db:text($db, $key)/.... }; Best, Christian
participants (2)
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Andy Bunce -
Christian Grün