Offer close und update methods for TextIndexingService

[forum-is]

Proposal

The interface for TextIndexingService should offer a close() method which would be called within db.close(). This would allow a proper shutdown for external fulltext indexers by implementing this method.

Also, an additional update() method would be beneficial to possibly force any internal updates.

Use case

When using Apache Lucene as a third-party fulltext index with a filesystem indexer, forcibly committing changes immediately after updating each field results in very poor performance. Lucene already offers mechanisms that commit changes when either its memory buffer is full (default) and/or a certain threshold of uncommitted documents is present (optional).

However, to ensure that all pending changes are properly persisted, commit() has to be called on shutdown.

The update() method could ensure consistency after bulk updates or could even be called periodically from outside the indexing service.