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From "Marcelo F. Ochoa (JIRA)" <>
Subject [jira] Created: (LUCENE-724) Oracle JVM implementation for Lucene DataStore also a preliminary implementation for an Oracle Domain index using Lucene
Date Wed, 22 Nov 2006 23:45:02 GMT
Oracle JVM implementation for Lucene DataStore also a preliminary implementation for an Oracle
Domain index using Lucene

                 Key: LUCENE-724
             Project: Lucene - Java
          Issue Type: New Feature
          Components: Store
    Affects Versions: 2.0.0
         Environment: Oracle 10g R2 with latest patchset, there is a txt file into the lib
directory with the required libraries to compile this extension, which for legal issues I
can't redistribute. All these libraries are include into the Oracle home directory,
            Reporter: Marcelo F. Ochoa
            Priority: Minor

Here a preliminary implementation of the Oracle JVM Directory data store which replace a file
system by BLOB data storage.
The reason to do this is:
  - Using traditional File System for storing the inverted index is not a good option for
some users.
  - Using BLOB for storing the inverted index running Lucene outside the Oracle database has
a bad performance because there are a lot of network round trips and data marshalling.
  - Indexing relational data stores such as tables with VARCHAR2, CLOB or XMLType with Lucene
running outside the database has the same problem as the previous point.
  - The JVM included inside the Oracle database can scale up to 10.000+ concurrent threads
without memory leaks or deadlock and all the operation on tables are in the same memory space!!
  With these points in mind, I uploaded the complete Lucene framework inside the Oracle JVM
and I runned the complete JUnit test case successful, except for some test such as the RMI
test which requires special grants to open ports inside the database.
  The Lucene's test cases run faster inside the Oracle database (11g) than the Sun JDK 1.5,
because the classes are automatically JITed after some executions.
  I had implemented and OJVMDirectory Lucene Store which replaces the file system storage
with a BLOB based storage, compared with a RAMDirectory implementation is a bit slower but
we gets all the benefits of the BLOB storage (backup, concurrence control, and so on).
 The OJVMDirectory is cloned from the source at (DBDirectory) but with some changes to run
faster inside the Oracle JVM.
 At this moment, I am working in a full integration with the SQL Engine using the Data Cartridge
API, it means using Lucene as a new Oracle Domain Index.
 With this extension we can create a Lucene Inverted index in a table using:

create index it1 on t1(f2) indextype is LuceneIndex parameters('test');

 assuming that the table t1 has a column f2 of type VARCHAR2, CLOB or XMLType, after this,
the query against the Lucene inverted index can be made using a new Oracle operator:

select * from t1 where contains(f2, 'Marcelo') = 1;

 the important point here is that this query is integrated with the execution plan of the
Oracle database, so in this simple example the Oracle optimizer see that the column "f2" is
indexed with the Lucene Domain index, then using the Data Cartridge API a Java code running
inside the Oracle JVM is executed to open the search, a fetch all the ROWID that match with
"Marcelo" and get the rows using the pointer,
here the output:

SELECT STATEMENT                                      ALL_ROWS      3       1       115
       TABLE ACCESS(BY INDEX ROWID) LUCENE.T1          3       1       115

 Another benefits of using the Data Cartridge API is that if the table T1 has insert, update
or delete rows operations a corresponding Java method will be called to automatically update
the Lucene Index.
  There is a simple HTML file with some explanation of the code.
   The install.sql script is not fully tested and must be lunched into the Oracle database,
not remotely.
  Best regards, Marcelo.

- For Oracle users the big question is, Why do I use Lucene instead of Oracle Text which is
implemented in C?
  I think that the answer is too simple, Lucene is open source and anybody can extend it and
add the functionality needed
- For Lucene users which try to use Lucene as enterprise search engine, the Oracle JVM provides
an highly scalable container which can scale up to 10.000+ concurrent session and with the
facility of querying table in the same memory space.

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