Lucene vs Solr

Many people new to Lucene and Solr will ask the obvious question: Should I use Lucene or Solr?

The answer is simple: if you're asking yourself this question, in 99% of situations, what you want to use is Solr.

A simple way to conceptualize the relationship between Solr and Lucene is that of a car and its engine. You can't drive an engine, but you can drive a car. Similarly, Lucene is a programmatic library which you can't use as-is, whereas Solr is a complete application which you can use out-of-box.

What is Solr?

Apache Solr is a web application built around Lucene with all kinds of goodies.

It adds functionality like

• XML/HTTP and JSON APIs
• Hit highlighting
• Faceted Search and Filtering
• Geospatial Search
• Fast Incremental Updates and Index Replication
• Caching
• Replication
• Web administration interface etc

Unlike Lucene, Solr is a web application (WAR) which can be deployed in any servlet container, e.g. Jetty, Tomcat, Resin, etc.

Solr can be installed and used by non-programmers. Lucene cannot.

Is it well supported?

Yes! The Solr community is very vibrant and helpful.

Can Solr indexes be read by Lucene and vice-versa?

Since Solr uses Lucene under the hood, Solr indexes and Lucene indexes are one and the same thing.

There is technically no such thing as a Solr index, only a Lucene index created by a Solr instance.

When should I use Lucene then?

If you need to embed search functionality into a desktop application for example, Lucene is the more appropriate choice.

For situations where you have very customized requirements requiring low-level access to the Lucene API classes, Solr may be more a hindrance than a help, since it is an extra layer of indirection.