[LUCENE-8489] Provide List type constructors for BaseCompositeReader based Readers

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Won't Fix
• Component/s: core/index
• Labels: usability
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Namgyu Kim
• Created: 06/Sep/18 17:25
• Updated: 28/Aug/22 15:35
• Resolved: 18/Dec/19 13:45

Description

Currently, Reader based on BaseCompositeReader(MultiReader, ParallelCompositeReader, DirectoryReader) does not support List type constructor.

In fact, this does not make a big difference in performance, but users will think positively if the API supports more variants.

I will add the following to support this.

1) MultiReader

public MultiReader(List<IndexReader> subReaders) throws IOException {
  this(subReaders, true);
}

public MultiReader(List<IndexReader> subReaders, boolean closeSubReaders) throws IOException {
  this(subReaders.toArray(new IndexReader[0]), closeSubReaders);
}

2) ParallelCompositeReader

public ParallelCompositeReader(List<CompositeReader> readers) throws IOException {
  this(true, readers);
}

public ParallelCompositeReader(boolean closeSubReaders, List<CompositeReader> readers) throws IOException {
  this(closeSubReaders, readers, readers);
}

public ParallelCompositeReader(boolean closeSubReaders, List<CompositeReader> readers, List<CompositeReader> storedFieldReaders) throws IOException {
  this(closeSubReaders, readers.toArray(new CompositeReader[0]), storedFieldReaders.toArray(new CompositeReader[0]));
}

3) DirectoryReader

protected DirectoryReader(Directory directory, List<LeafReader> segmentReaders) throws IOException {
  super(segmentReaders);
  this.directory = directory;
}

4) BaseCompositeReader

@SuppressWarnings("unchecked")
protected BaseCompositeReader(List<R> subReaders) throws IOException {
  this(subReaders.toArray((R[]) new IndexReader[subReaders.size()]));
}

5) Test
I wrote a test case in "TestParallelCompositeReader".

If you have any questions or requests, please left any comments