Introduction to Search and Indexing

Suppose you’re developing a data-driven application. You anticipate that your application will have to store a huge number of database records. You could provide some canned queries to your users, but you know you can’t mind-read every way they’ll want to find their data. Why not create an index for your custom entities so they can search against the index? Liferay’s search and indexing functionality is provided by Lucene, a Java search framework. Lucene works by converting searchable entities into documents. Lucene documents are not documents in the ordinary English sense of the word. Rather, they are custom objects that correspond to searchable entities. When a Lucene index is searched, a hits object is returned that contains pointers to the documents that match the search query. Searching for guestbook entries using an index can be faster than searching for entities in the database. If an indexed document contains the data you’re interested in, you can avoid having to make a database query altogether.

Suppose, for example, that you want to retrieve custom entities that have specific values in specific fields. Without an index, you’d have to retrieve all of the custom entities from the database and check the specific fields of each entity for the specific values. With an index, you just have to search the indexed documents’ specific fields for the specific values. Once you have the matching documents in the index, you can retrieve the values of any other fields of the matching documents. If you need to, you can run a database query to retrieve the entities that correspond to the indexed documents. This database query should be much less expensive than a query that has to retrieve all the custom entities. In this section of tutorials, you’ll explore Liferay’s search and indexing APIs and learn how to use them in your applications.

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