MergeScheduler (Lucene 10.5.0 core API)
Description: declaration: package: org.apache.lucene.index, class: MergeScheduler

Package org.apache.lucene.index

# Class MergeScheduler

java.lang.Object
org.apache.lucene.index.MergeScheduler

All Implemented Interfaces:
  `Closeable`, `AutoCloseable`

Direct Known Subclasses:
  `ConcurrentMergeScheduler`, `NoMergeScheduler`, `SerialMergeScheduler`

public abstract class MergeScheduler extends Object implements Closeable
Expert: `IndexWriter` uses an instance implementing this interface to execute the merges selected by a `MergePolicy`. The default MergeScheduler is `ConcurrentMergeScheduler`.

WARNING: This API is experimental and might change in incompatible ways in the next release.

- ## Nested Class Summary

  Nested Classes
  Modifier and Type
  Class
  Description
  `static interface`
  `MergeScheduler.MergeSource`
  Provides access to new merges and executes the actual merge

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `protected InfoStream`
  `infoStream`
  For messages about merge scheduling

- ## Constructor Summary

  Constructors
  Modifier
  Constructor
  Description
  `protected`
  `MergeScheduler()`
  Sole constructor.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `close()`
  Close this MergeScheduler.
  `Executor`
  `getIntraMergeExecutor(MergePolicy.OneMerge merge)`
  Provides an executor for parallelism during a single merge operation.
  `abstract void`
  `merge(MergeScheduler.MergeSource mergeSource, MergeTrigger trigger)`
  Run the merges provided by `MergeScheduler.MergeSource.getNextMerge()`.
  `protected void`
  `message(String message)`
  Outputs the given message - this method assumes `verbose()` was called and returned true.
  `protected boolean`
  `verbose()`
  Returns true if infoStream messages are enabled.
  `Directory`
  `wrapForMerge(MergePolicy.OneMerge merge, Directory in)`
  Wraps the incoming `Directory` so that we can merge-throttle it using `RateLimitedIndexOutput`.

  ### Methods inherited from class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Field Details

  - ### infoStream

    protected InfoStream infoStream
    For messages about merge scheduling

- ## Constructor Details

  - ### MergeScheduler

    protected MergeScheduler()
    Sole constructor. (For invocation by subclass constructors, typically implicit.)

- ## Method Details

  - ### merge

    public abstract void merge(MergeScheduler.MergeSource mergeSource, MergeTrigger trigger) throws IOException
    Run the merges provided by `MergeScheduler.MergeSource.getNextMerge()`.
    Parameters:
      `mergeSource` - the `IndexWriter` to obtain the merges from.
      `trigger` - the `MergeTrigger` that caused this merge to happen
    Throws:
      `IOException`

  - ### wrapForMerge

    public Directory wrapForMerge(MergePolicy.OneMerge merge, Directory in)
    Wraps the incoming `Directory` so that we can merge-throttle it using `RateLimitedIndexOutput`.

  - ### getIntraMergeExecutor

    public Executor getIntraMergeExecutor(MergePolicy.OneMerge merge)
    Provides an executor for parallelism during a single merge operation. By default, the method returns a `SameThreadExecutorService` where all intra-merge actions occur in their calling thread.

  - ### close

    public void close() throws IOException
    Close this MergeScheduler.
    Specified by:
      `close` in interface `AutoCloseable`
    Specified by:
      `close` in interface `Closeable`
    Throws:
      `IOException`

  - ### verbose

    protected boolean verbose()
    Returns true if infoStream messages are enabled. This method is usually used in conjunction with `message(String)`:

         if (verbose()) {
           message("your message");
         }

  - ### message

    protected void message(String message)
    Outputs the given message - this method assumes `verbose()` was called and returned true.