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From Andrius Juozapaitis <andri...@gmail.com>
Subject integrating lucene with ibatis - advice wanted
Date Tue, 16 Mar 2010 12:35:57 GMT
Hey guys,

I created a framework I plan to use for a few projects in-house, using
ibatis 3. I enjoy the separation of sql, mapping and domain objects, but I
have a pretty complex domain model (first class objects may have any number
of attributes, hierarchical if neccessary), so writing sql and taking care
of things like sorting and paging gets really hard, and screws up the
performance. I tried using apache lucene to take the actual searches off my
hands, and it works like a charm. I annotate  the domain objects with
@Indexable annotations, and pass the mapper name (which is retrieved from
the spring context), that can query the objects from the db, and index the
properties and attributes of the first class objects accordingly *on the
application startup*. This builds an index in memory, and the lucene queries
just return the IDs of the matching documents, sorted and filtered, and with
convenient things like totalCount for paging implementation. The actual data
can then be retrieved by simply querying by the primary keys from the
relevant tables.
Now, there is the issue of how to synchronize the database state with the
lucene index. I see a few ways to implement this:
1. Mark the mapper methods that are supposed to change the state of the
database with a marker annotation, and create an aspect that intercepts
those calls, and updates the lucene index.
This has a nasty side effect, that if someone changes the data in the db
directly, index won't know about it until the application is restarted, but
technically, I can live with that.
2. Create an aspect, that intercepts certain calls in the Ibatis layer, and
depending on the operation at hand (insert, update, delete), updates the
lucene index. Beats annotating the methods, and is semi-automatic. Not sure
at which layer I should intercept this, though - hence, if there's a
definite place to hang this aspect on, I'm all ears.
3. Create database triggers, that would fire the events on
insert/update/delete using JMS or any other communication mechanism. This is
probably the best way to go (my objects have well defined identities), but
requires a lot of coding, and would kill the performance on update-heavy
operations (imports and such), as the network roundtrip will be required
from app server->db  server->[app server->db server]->app server (square
brackets representing the call of the lucene index update by the trigger),
not to mention the hurdles of setting up JMS producer in postgres
environment...

There are probably other ways to implement this - I would be very grateful
if you guys could share your insights on this.

Thanks in advance,
Andrius

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