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Chapter 6. Manual indexing

6.1. Indexing
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It is sometimes useful to index an entity even if this entity is not inserted or updated to the database. This is for example the case when you want to build your index for the first time. FullTextSession.index() allows you to do so.

Example 6.1. Indexing an entity via FullTextSession.index()

FullTextSession fullTextSession = Search.getFullTextSession(session);
Transaction tx = fullTextSession.beginTransaction();
for (Customer customer : customers) {
    fullTextSession.index(customer);
}
tx.commit(); //index are written at commit time
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For maximum efficiency, Hibernate Search batches index operations and executes them at commit time. If you expect to index a lot of data, however, you need to be careful about memory consumption since all documents are kept in a queue until the transaction commit. You can potentially face an OutOfMemoryException. To avoid this exception, you can use fullTextSession.flushToIndexes(). Every time fullTextSession.flushToIndexes() is called (or if the transaction is committed), the batch queue is processed (freeing memory) applying all index changes. Be aware that once flushed changes cannot be rolled back.

Note

hibernate.search.worker.batch_size has been deprecated in favor of this explicit API which provides better control
Other parameters which also can affect indexing time and memory consumption are:
  • hibernate.search.[default|<indexname>].indexwriter.[batch|transaction].max_buffered_docs
  • hibernate.search.[default|<indexname>].indexwriter.[batch|transaction].max_field_length
  • hibernate.search.[default|<indexname>].indexwriter.[batch|transaction].max_merge_docs
  • hibernate.search.[default|<indexname>].indexwriter.[batch|transaction].merge_factor
  • hibernate.search.[default|<indexname>].indexwriter.[batch|transaction].ram_buffer_size
  • hibernate.search.[default|<indexname>].indexwriter.[batch|transaction].term_index_interval
These parameters are Lucene specific and Hibernate Search is just passing these parameters through - see Section 3.8, “Tuning Lucene indexing performance” for more details.

Example 6.2. Efficiently indexing a given class (useful for index (re)initialization)

fullTextSession.setFlushMode(FlushMode.MANUAL);
fullTextSession.setCacheMode(CacheMode.IGNORE);
transaction = fullTextSession.beginTransaction();
//Scrollable results will avoid loading too many objects in memory
ScrollableResults results = fullTextSession.createCriteria( Email.class )
    .setFetchSize(BATCH_SIZE)
    .scroll( ScrollMode.FORWARD_ONLY );
int index = 0;
while( results.next() ) {
    index++;
    fullTextSession.index( results.get(0) ); //index each element
    if (index % BATCH_SIZE == 0) {
        fullTextSession.flushToIndexes(); //apply changes to indexes
        fullTextSession.clear(); //clear since the queue is processed
    }
}
transaction.commit();
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Try to use a batch size that guarantees that your application will not run out of memory.
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