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org.apache.lucene.search.IndexSearcher  IndexSearcher

org.apache.lucene.index.CompositeReader getContext

org.apache.lucene.index.CompositeReaderContext create

org.apache.lucene.index.CompositeReaderContext build 

    private IndexReaderContext build(CompositeReaderContext parent, IndexReader reader, int ord, int docbase) {
      if (reader instanceof LeafReader) {
        final LeafReader ar = (LeafReader) reader;
        final LeafReaderContext atomic = new LeafReaderContext(parent, ar, ord, docbase, leaves.size(), leafDocbase);
        leaves.add(atomic);
        leafDocbase += reader.maxDoc();
        return atomic;
      } else {
        final CompositeReader cr = (CompositeReader) reader;
        final List sequentialSubReaders = cr.getSequentialSubReaders();
        final List children = Arrays.asList(new IndexReaderContext[sequentialSubReaders.size()]);
        final CompositeReaderContext newParent;
        if (parent == null) {
          newParent = new CompositeReaderContext(cr, children, leaves);
        } else {
          newParent = new CompositeReaderContext(parent, cr, ord, docbase, children);
        }
        // docbase是累加来的
        int newDocbase = 0;
        for (int i = 0, c = sequentialSubReaders.size(); i < c; i++) {
          final IndexReader r = sequentialSubReaders.get(i);
            // 此处有个递归
          children.set(i, build(newParent, r, i, newDocbase));
          newDocbase += r.maxDoc();
        }
        assert newDocbase == cr.maxDoc();
        return newParent;
      }
    }