Someone on the list gave me following tip:
*********************************************************
for $i in index-scan("chemicalcontent_id", "", "GE")/@id return string($i) - as 
a result, you will get the keyset of an index, maybe with duplicate keys (if 
they are presented in index), which can be removed with distinct-values 
function. 

Here, the blank key to compare with ( "" ) assumed to be less than any other 
key in index.
*********************************************************

But I tried that and it still is not responsive.  I think Sedna is not using 
the index only but still doing a full collection scan. Can someone shed some 
light on this?

I was also looking a bit into the documentation for how to run an explain plan. 
But to my surprise I don't see anything back of index usage. It's something I 
would typically expect from an explain plan.  

http://www.sedna.org/progguide/ProgGuidesu10.html#x16-640002.7.3



To give an example, I have following index and xquery module
*******************************************************************
create index "package_id"
  on fn:collection("packages/released")/Package
  by @identifier
  as xs:string
*******************************************************************
module namespace packages = "http://www.nxp.com/packages";;

declare function packages:getPackage($id as xs:string) as element(Package)? {
    index-scan('package_id', $id, 'EQ')
};
*******************************************************************

Now I tried to explain a method invocation that uses a index:
*******************************************************************
explain
import module namespace packages = "http://www.nxp.com/packages";;
packages:getPackage("SOT669")
*******************************************************************

It shows me following explanation, but no evidence of an index being used.
*******************************************************************
<prolog xmlns="http://www.modis.ispras.ru/sedna"/>
<query xmlns="http://www.modis.ispras.ru/sedna";>
  <operation name="PPQueryRoot">
    <operation name="PPFunCall" id="0" function-name="packages:getPackage" 
position="3:1">
      <operation name="PPConst" type="xs:string" value="SOT669" 
position="3:21"/>
    </operation>
  </operation>
</query>
*******************************************************************


So any tips on debugging my performance problem are very welcome !!

Thx in advance,
Robby

-----Original Message-----
From: Robby Pelssers [mailto:robby.pelss...@nxp.com] 
Sent: Thursday, January 10, 2013 12:09 PM
To: sedna-discussion@lists.sourceforge.net
Subject: [Sedna-discussion] poor performance for large collection

Hi all,

I have a single collection of 24468 documents. 

<count>{count(collection("chemicalContent/released")/TypeName)}</count>  == 
24468

When I just try to run below statement it takes very long to execute. The 
documents themselves are not even that big varying between 2kb and 12kb.

for $i in collection("chemicalContent/released") return document-uri($i)

I also have a index on that collection:

create index "chemicalcontent_id"
  on fn:collection("chemicalContent/released")/TypeName
  by @id
  as xs:string

Is it normal for that statement to execute that long   (> 1 minute) ?


Is there a way to perhaps speed up fetching a list of all @id's for that 
particular collection?

Thx in advance,
Robby


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