[LUCENE-7983] Make IndexReaderWarmer a functional interface

• Type: Improvement
• Status: Closed
• Priority: Trivial
• Resolution: Fixed
• Fix Version/s: 7.1
• Lucene Fields: New
• Assignee: Dawid Weiss
• Reporter: Dawid Weiss
• Created: 03/Oct/17 09:05
• Updated: 28/Aug/22 15:19
• Resolved: 07/Oct/17 07:45

Description

IndexReaderWarmer has a single method but is an abstract class with a confusing protected constructor. Can we make it a proper functional interface instead? This is marked as lucene.experimental API and while it would be a binary incompatibility, everything remains the same at the source level, even for existing implementations.

public static abstract class IndexReaderWarmer {
    /** Sole constructor. (For invocation by subclass 
     *  constructors, typically implicit.) */
    protected IndexReaderWarmer() {
    }

    /** Invoked on the {@link LeafReader} for the newly
     *  merged segment, before that segment is made visible
     *  to near-real-time readers. */
    public abstract void warm(LeafReader reader) throws IOException;
  }