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From "J. Delgado" <jdelg...@lendingclub.com>
Subject Oracle-Lucene integration (OJVMDirectory and Lucene Domain Index) - LONG
Date Thu, 13 Sep 2007 22:27:24 GMT
I'm very happy to announce the partial rework and extension to LUCENE-724
(Oracle-Lucene Integration), primarily based on new requirements from
LendingClub.com, who commissioned the work to Marcelo Ochoa, the contributer
of the original patch (great job Marcelo!). As contribution of
LendingClub.com to the Lucene community we have posted the code on a public
CVS (sourceforge) as explained below.

Here at Lending Club (www.lendingclub.com) we have very specific needs
regarding the indexing of both structured and unstructured data, most of it
transactional in nature and siting in our Oracle !0gR2 DB, with a highly
complex schema. Our "ranking" of loans in the inventory includes components
of exact, textual and hardcore mathematical calculations including time,
amount and spatial constraints. This integration of Lucene into Oracle as a
Domain Index will now allow us to query this inventory in real-time. Going
against the Lucene index, created on "synthetic documents" comprised of
fields being populated from diverse tables (user data store), eliminates the
need to create very complex joins to link data from different tables at
query time. This, along with the support of the full Lucene query language,
makes this a great alternative to:

   1. Using Lucene outside the database which requires "crawling" the
   data and storing the index outside the database, loosing all the benefits of
   a fully transactional system and a secure environment.
   2. Using Oracle Text, which is very powerful but lacks the
   extensibility and flexibility that Lucene offers (for example, being able to
   query directly the index from the Java layer or implementing our our ranking
   algorithm), though to be completely fair some of it is addressed in the new
   Oracle DB 11g version.

If anyone is interested in learning more how we are going to use this within
Lending Club, please drop me a line. BTW, please make sure you check us out:
"Lending Club (http://www.lendingclub.com/), the rapidly growing
people-to-people (P2P) lending service that launched as a Facebook
application in May 2007, today announced the public availability of its
services with the launch of LendingClub.com. Lending Club connects lenders
and borrowers based upon shared affinities, enabling them to bypass banks to
secure better interest rates on loans"... more about the announcement here
http://www.sys-con.com/read/428678.htm. We have seen man entrepreneurs
applying for loans and being helped by regular people to build their
business with the money obtained at very low interest.

OK, without further marketing stuff (sorry for that), here is the original
note sent to me by Marcelo that summarizes all the new cool functionalities:

OJVMDirectory, a Lucene Integration running inside the Oracle JVM is going
one step further.

This new release includes:

   - Synchronized with latest Lucene 2.2.0 production
   - Replaced in memory storage using Vector based implementation by
   direct BLOB IO, reducing memory usage for large index.
   - Support for user data stores, it means you can not only index one
   column at time (limited by Data Cartridge API on 10g), now you can index
   multiples columns at base table and columns on related tabled joined
   together.
   - User Data Stores can be customized by the user, it means writing a
   simple Java Class users can control which column are indexed, padding
   - used or any other functionality previous to document adding step.
   - There is a DefaultUserDataStore which gets all columns of the query
   and built a Lucene Document with Fields representing each database
   - columns these fields are automatically padded if they have NUMBER or
   rounded if they have DATE data, for example.
   - lcontains() SQL operator support full Lucene's QueryParser syntax to
   provide access to all columns indexed, see examples below.
   - Support for DOMAIN_INDEX_SORT and FIRST_ROWS hint, it means that if
   you want to get rows order by lscore() operator (ascending,descending) the
   optimizer hint will assume that Lucene Domain Index will returns rowids in
   proper order avoided an inline-view to sort it.
   - Automatic index synchronization by using AQ's Call Back.
   - Lucene Domain Index creates extra tables named IndexName$T and an
   Oracle AQ named IndexName$Q with his storage table IndexName$QT at user's
   schema, so you can alter storage's preference if you want.
   - ojvm project is at SourceForge.net CVS, so anybody can get it and
   collaborate ;)
   - Tested against 10gR2 and 11g database.


Some sample usages:

create table t2 (
 f4 number primary key,
 f5 VARCHAR2(200));
create table t1 (
 f1 number,
 f2 CLOB,
 f3 number,
 CONSTRAINT t1_t2_fk FOREIGN KEY (f3)
     REFERENCES t2(f4) ON DELETE cascade);
create index it1 on t1(f3) indextype is lucene.LuceneIndex
 parameters('Analyzer:org.apache.lucene.analysis
.SimpleAnalyzer;ExtraCols:f2');

alter index it1
parameters('ExtraCols:f2,t2.f5;ExtraTabs:t2;WhereCondition:t1.f3=t2.f4;DecimalFormat:000');


Lucene domain index will store f2 and f3 columns of table t1 plus f5 of
table t2.

So you can query then with:

 select lscore(1),f2 from t1 where lcontains(f3, 'f2:test',1) > 0;
or
 select lscore(1),f2 from t1 where lcontains(f3, 'f2:test and f3:[001 to
200]',1) > 0;

 select /*+ DOMAIN_INDEX_SORT */ lscore(1),f2,t2.f5
 from t1,t2
 where lcontains(f3, 'f2:test1 and f3:[001 to 200] and t2.f5:test2',1) > 0
 and t1.f3=t2.f4
 order by lscore(1) asc;

In latest example Oracle's optimizer will assume that Lucene Domain Index
will resolve first a set of rowid matching "f2:test1 and f3:[001 to 200] and
t2.f5:test2" then will direct access by by index rowid on table t1 and
perform the join with t2.

More examples and information can be found at:
http://dbprism.cvs.sourceforge.net/dbprism/ojvm/Readme.txt?revision=1.10&view=markup

--
Marcelo F. Ochoa
http://marcelo.ochoa.googlepages.com/home

Cheers!

Joaquin Delgado, PhD
CTO, Lending Club
www.lendingclub.com

 <http://marcelo.ochoa.googlepages.com/home>

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