## org.apache.lucene.search
Class SearcherManager

    java.lang.Object
      org.apache.lucene.search.ReferenceManager<IndexSearcher>
          org.apache.lucene.search.SearcherManager

All Implemented Interfaces:
  Closeable

    public final class SearcherManager

extends ReferenceManager<IndexSearcher>

Utility class to safely share `IndexSearcher` instances across multiple threads, while periodically reopening. This class ensures each searcher is closed only once all threads have finished using it.

Use `ReferenceManager.acquire()` to obtain the current searcher, and `ReferenceManager.release(G)` to release it, like this:

     IndexSearcher s = manager.acquire();
     try {
       // Do searching, doc retrieval, etc. with s
     } finally {
       manager.release(s);
     }
     // Do not use s after this!
     s = null;

In addition you should periodically call `ReferenceManager.maybeRefresh()`. While it's possible to call this just before running each query, this is discouraged since it penalizes the unlucky queries that do the reopen. It's better to use a separate background thread, that periodically calls maybeReopen. Finally, be sure to call `ReferenceManager.close()` once you are done.

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

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.search.ReferenceManager
`ReferenceManager.RefreshListener`

Field Summary

Fields inherited from class org.apache.lucene.search.ReferenceManager
`current`

Constructor Summary
`SearcherManager(Directory dir, SearcherFactory searcherFactory)` Creates and returns a new SearcherManager from the given `Directory`.
`SearcherManager(IndexWriter writer, boolean applyAllDeletes, SearcherFactory searcherFactory)` Creates and returns a new SearcherManager from the given `IndexWriter`.

Method Summary
`protected void` `decRef(IndexSearcher reference)` Decrement reference counting on the given reference.
`static IndexSearcher` `getSearcher(SearcherFactory searcherFactory, IndexReader reader)` Expert: creates a searcher from the provided `IndexReader` using the provided `SearcherFactory`.
`boolean` `isSearcherCurrent()` Returns `true` if no changes have occured since this searcher ie.
`protected IndexSearcher` `refreshIfNeeded(IndexSearcher referenceToRefresh)` Refresh the given reference if needed.
`protected boolean` `tryIncRef(IndexSearcher reference)` Try to increment reference counting on the given reference.

Methods inherited from class org.apache.lucene.search.ReferenceManager
`acquire, addListener, afterClose, afterMaybeRefresh, close, maybeRefresh, maybeRefreshBlocking, release, removeListener`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### SearcherManager

    public SearcherManager(IndexWriter writer,
                           boolean applyAllDeletes,
                           SearcherFactory searcherFactory)
                    throws IOException

  Creates and returns a new SearcherManager from the given `IndexWriter`.

  Parameters:
    `writer` - the IndexWriter to open the IndexReader from.
    `applyAllDeletes` - If `true`, all buffered deletes will be applied (made visible) in the `IndexSearcher` / `DirectoryReader`. If `false`, the deletes may or may not be applied, but remain buffered (in IndexWriter) so that they will be applied in the future. Applying deletes can be costly, so if your app can tolerate deleted documents being returned you might gain some performance by passing `false`. See `DirectoryReader.openIfChanged(DirectoryReader, IndexWriter, boolean)`.
    `searcherFactory` - An optional `SearcherFactory`. Pass `null` if you don't require the searcher to be warmed before going live or other custom behavior.
  Throws:
    `IOException` - if there is a low-level I/O error

### SearcherManager

    public SearcherManager(Directory dir,
                           SearcherFactory searcherFactory)
                    throws IOException

  Creates and returns a new SearcherManager from the given `Directory`.

  Parameters:
    `dir` - the directory to open the DirectoryReader on.
    `searcherFactory` - An optional `SearcherFactory`. Pass `null` if you don't require the searcher to be warmed before going live or other custom behavior.
  Throws:
    `IOException` - if there is a low-level I/O error

Method Detail

### decRef

    protected void decRef(IndexSearcher reference)
                   throws IOException

  Description copied from class: `ReferenceManager`
  Decrement reference counting on the given reference.

  Specified by:
    `decRef` in class `ReferenceManager<IndexSearcher>`
  Throws:
    `IOException` - if reference decrement on the given resource failed.

### refreshIfNeeded

    protected IndexSearcher refreshIfNeeded(IndexSearcher referenceToRefresh)
                                     throws IOException

  Description copied from class: `ReferenceManager`
  Refresh the given reference if needed. Returns `null` if no refresh was needed, otherwise a new refreshed reference.

  Specified by:
    `refreshIfNeeded` in class `ReferenceManager<IndexSearcher>`
  Throws:
    `IOException` - if the refresh operation failed

### tryIncRef

    protected boolean tryIncRef(IndexSearcher reference)

  Description copied from class: `ReferenceManager`
  Try to increment reference counting on the given reference. Return true if the operation was successful.

  Specified by:
    `tryIncRef` in class `ReferenceManager<IndexSearcher>`

### isSearcherCurrent

    public boolean isSearcherCurrent()
                              throws IOException

  Returns `true` if no changes have occured since this searcher ie. reader was opened, otherwise `false`.

  Throws:
    `IOException`
  See Also:
    `DirectoryReader.isCurrent()`

### getSearcher

    public static IndexSearcher getSearcher(SearcherFactory searcherFactory,
                                            IndexReader reader)
                                     throws IOException

  Expert: creates a searcher from the provided `IndexReader` using the provided `SearcherFactory`. NOTE: this decRefs incoming reader on throwing an exception.

  Throws:
    `IOException`

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