I didn't say that PG would refuse to use any system that was developed in Java. What I meant that he would never would put himself in a situation where the application would depend on Java for development, or to add more features.

To integrate with Google, you talk HTTP, not Java. To adopt Lucene, you'll have to talk Java. There is quite some difference, isn't it?

You can push everything you want indexed into SOLR by HTTP -- so even though it's Java/Lucene you don't have to get your hands dirty.

They use some Java, but a whole lot more Python and C++...