Re: [Sedna-discussion] poor performance for large collection

[Robby P. <Rob...@nx...>]

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:rob...@nx...] 
Sent: Thursday, January 10, 2013 12:09 PM
To: sed...@li...
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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