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From Todd Nine <t...@spidertracks.co.nz>
Subject RE: Help with Numeric Range
Date Wed, 23 Jun 2010 23:59:57 GMT
Hi Uwe,

  Thank you for your help, it is greatly appreciated.  Unfortunately, my
tests all fail except for RangeInclusive.  I've changed the step to be 6
as per your recommendation.  I had it at max to eliminate step precision
as the cause of the test failure.  Essentially, all keys in Cassandra
are UTF-8 Keys.  In the Lucandra, the keys are constructed in the
following way.

1. Get the token stream for the field.  In this case it's a
NumericTokenStream with (numeric,valSize=64,precisionStep=6)
2. For all tokens in the stream, create a UTF8 String in the following
format <fieldname>\uffff<token value>
3. Set the term frequency to 1

This gives us a list of tokens, prefixed with the field name and the
delimiter.  then we do this

for each term from above create a key of the format
<indexname>\uffff<fieldname>\uffff<token value> and write it to TermInfo
column Family

After debugging the implementation of the LucandraTermEnum, it is
correctly returning values that should match my numeric range query.
However, I never get the results in the TopDocs result set after they're
handed back to the numeric range query object.  Any ideas why this is
happening?

Thanks,
Todd




On Wed, 2010-06-23 at 08:53 +0200, Uwe Schindler wrote:

> Hi Todd,
> 
> I am not sure if I understand your problem correctly. I am not familiar with Lucandra/Cassandra
at all, but if Lucandra implements the IndexWriter and IndexReader according to the documentation,
numeric queries should work. A NumericField internally creates a TokenStream and "analyzes"
the number to several Tokens, which are somehow "half binary" (they are terms containing of
characters in the full 0..127 range for optimal UTF8 compression with 3.x versions of Lucene).
The exact encoding can be looked at in the NumericUtils class + javadocs.
> 
> About your testcase: The test looks good, so does it fail? If yes, where is the problem?
You can also look into Lucene's test TestNumericRangeQuery64 for more examples. Or modify
its @BeforeClass to instead build a Lucandra index. 
> 
> The test has one thing, that is not intended to be done like that:
> numeric = new NumericField("long", Integer.MAX_VALUE, Store.YES, true);
> 
> You are using MAX_VALUE as precision step, this would slowdown all queries to the speed
of old-style TermRangeQueries. It is always better to stick with the default of 4, which creates
64 bits / 4 precStep = 16 terms per value. Alternatively for longs, 6 is a good precision
step (see NumericRangeQuery documentation). MAX_VALUE is only intended for fields that do
not do numeric ranges but e.g. sort only. precisionStep is a performance tuning parameter,
it has nothing to do with better/worse precision on terms or different query results. If you
are using NumericRangeQuery with this large precStep, you are not using the numeric features
at all, so your test should not behave different from a conventional TermRangeQuery with padded
terms.
> 
> Uwe
> 
> -----
> Uwe Schindler
> H.-H.-Meier-Allee 63, D-28213 Bremen
> http://www.thetaphi.de
> eMail: uwe@thetaphi.de
> 
> 
> > -----Original Message-----
> > From: Todd Nine [mailto:todd@spidertracks.co.nz]
> > Sent: Wednesday, June 23, 2010 7:53 AM
> > To: java-user@lucene.apache.org
> > Subject: Help with Numeric Range
> > 
> > Hi all,
> >   I'm new to Lucene, as well as Cassandra.  I'm working on the Lucandra
> > project to modify it to add some extra functionality.  It hasn't been fully
> > testing with range queries, so I've created some tests and contributed them.
> > You can view my source here.
> > 
> > http://github.com/tnine/Lucandra/blob/master/test/lucandra/NumericRang
> > eTests.java
> > 
> > First, is this a sensible test?  I'm specifically testing the case of longs where
I
> > need millisecond precision on my searches.
> > 
> > 
> > Second, I see that Numeric Fields are built via terms.  I think the issue lies in
> > the encoding of these terms into bytes for the Cassandra keys.  Can anyone
> > point me to some documentation on numeric queries and terms, and how
> > they are encoded at the byte level based on the precision?
> > 
> > Thanks,
> > Todd
> 

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