MultiIndex (Apache Jackrabbit 2.23.0-beta API)

java.lang.Object
- org.apache.jackrabbit.core.query.lucene.MultiIndex

```
public class MultiIndex
extends Object
```
A MultiIndex consists of a VolatileIndex and multiple PersistentIndexes. The goal is to keep most parts of the index open with index readers and write new index data to the volatile index. When the volatile index reaches a certain size (see SearchIndex.setMinMergeDocs(int)) a new persistent index is created with the index data from the volatile index, the same happens when the volatile index has been idle for some time (see SearchIndex.setVolatileIdleTime(int)). The new persistent index is then added to the list of already existing persistent indexes. Further operations on the new persistent index will however only require an IndexReader which serves for queries but also for delete operations on the index.
The persistent indexes are merged from time to time. The merge behaviour is configurable using the methods: SearchIndex.setMaxMergeDocs(int), SearchIndex.setMergeFactor(int) and SearchIndex.setMinMergeDocs(int). For detailed description of the configuration parameters see also the lucene IndexWriter class.
This class is thread-safe.
Note on implementation: Multiple modifying threads are synchronized on a MultiIndex instance itself. Synchronization between a modifying thread and reader threads is done using updateMonitor and updateInProgress.

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static class MultiIndex.Action
Defines an action on an MultiIndex.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`CachingMultiIndexReader`	`getIndexReader()`	Returns an read-only `IndexReader` that spans alls indexes of this `MultiIndex`.
`CachingMultiIndexReader`	`getIndexReader(boolean initCache)`	Returns an read-only `IndexReader` that spans alls indexes of this `MultiIndex`.

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

- Method Detail
  - getIndexReader
```
public CachingMultiIndexReader getIndexReader()
                                       throws IOException
```
    Returns an read-only IndexReader that spans alls indexes of this MultiIndex.
    
    Returns:
    
    an IndexReader.
    
    Throws:
    
    IOException - if an error occurs constructing the IndexReader.
  - getIndexReader
```
public CachingMultiIndexReader getIndexReader(boolean initCache)
                                       throws IOException
```
    Returns an read-only IndexReader that spans alls indexes of this MultiIndex.
    
    Parameters:
    
    initCache - when set true the hierarchy cache is completely initialized before this call returns.
    
    Returns:
    
    an IndexReader.
    
    Throws:
    
    IOException - if an error occurs constructing the IndexReader.