I was browsing some questions here concerning MySQL and faceted searches and I saw one response that suggested the use of Solr.
In my MySQL database, I have many tables
SOLR is a JAVA application but you can access it using any language that provides HTTP GET/POST functionality.
for your need you should refer to http://wiki.apache.org/solr/DataImportHandler but before jumping on the Indexing part go through the tutorial at lucene.apache.org /solr /tutorial.html
Take a look at data import handler. Apart from batch update you can also trigger update by calling update request handler. You would have to call it from your application but you can also create your own custom update request handler that would fit your needs.
If using data import handler, use the delta import command.