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From Alessandro <alessandro.bolo...@gmail.com>
Subject Re: XPath query performance question
Date Fri, 03 Feb 2012 15:11:37 GMT
If you were running the query without path restrictions, would it return more than one node?
In other words, outside the /companies tree, are there other company nodes with the same calais
attribute value?
Results are generated from the predicate, and then filtered by the path.


On Feb 3, 2012, at 7:13 AM, mslama@email.cz wrote:

> Hi,
> I have following use case:
> I have about 2000 company nodes under node companies:
> /companies/company[1]
> /companies/company[2]
> ....
> /companies/company[N]
> I query for one company by property value - exact match, no wildcards. And result should
contain just one node. For example I use query:
> //companies/company[@calais='http://d.opencalais.com/er/company/ralg-tr1r/2c970a55-e08d-3af8-ad1d-3c46f341e749']
> and then one call of NodeIterator.next to get unique (or first as there is no constraint
on uniqueness) result. So there is no big resultset.
> Property 'calais' is string type and when set it is unique ie. small number of company
nodes may have this property either empty or missing. Property value can be up to 100chars
long if it can make any difference for index.
> When only one thread is running it takes 100-200ms. When 4 threads are running it is
about 500ms on average. I used
> profiler with sampling to get some profiling data. I seems to be too much provided that
number on nodes is not that high
> and it is using Lucene index. Calls of query.execute and nodeIterator.next take both
about the same time.
> When I checked thread dumps it uses Lucene index so it does not look like it scans all
> Question: Is there any way how speedup this kind of lookup? The only way I found so far
is to incorporate the most often property used for lookup to node path as session.getNode(path)
is much faster.
> I use Jackrabbit 2.2.9 and Postgres 9.1 for saving all data but Lucene index. It runs
on JBoss 7.
> I searched for Jackrabbit XPath performance but no match for my use case: 
> a) exact property match without like/wildcards
> b) small resultset - just one result item
> Thanks
> Marek

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