org.apache.lucene.index.IndexReaderContext Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of org.apache.servicemix.bundles.lucene
This OSGi bundle wraps ${pkgArtifactId} ${pkgVersion} jar file.
There is a newer version: 6.4.2_1
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.lucene.index;

import java.util.List;

/**
 * A struct like class that represents a hierarchical relationship between {@link IndexReader}
 * instances.
 */
public abstract sealed class IndexReaderContext permits CompositeReaderContext, LeafReaderContext {
  /** The reader context for this reader's immediate parent, or null if none */
  public final CompositeReaderContext parent;

  /**
   * {@code true} if this context struct represents the top level reader within the hierarchical
   * context
   */
  public final boolean isTopLevel;

  /** the doc base for this reader in the parent, {@code 0} if parent is null */
  public final int docBaseInParent;

  /** the ord for this reader in the parent, {@code 0} if parent is null */
  public final int ordInParent;

  // An object that uniquely identifies this context without referencing
  // segments. The goal is to make it fine to have references to this
  // identity object, even after the index reader has been closed
  final Object identity = new Object();

  IndexReaderContext(CompositeReaderContext parent, int ordInParent, int docBaseInParent) {
    this.parent = parent;
    this.docBaseInParent = docBaseInParent;
    this.ordInParent = ordInParent;
    this.isTopLevel = parent == null;
  }

  /**
   * Expert: Return an {@link Object} that uniquely identifies this context. The returned object
   * does neither reference this {@link IndexReaderContext} nor the wrapped {@link IndexReader}.
   *
   * @lucene.experimental
   */
  public Object id() {
    return identity;
  }

  /** Returns the {@link IndexReader}, this context represents. */
  public abstract IndexReader reader();

  /**
   * Returns the context's leaves if this context is a top-level context. For convenience, if this
   * is an {@link LeafReaderContext} this returns itself as the only leaf, and it will never return
   * a null value.
   *
   * Note: this is convenience method since leaves can always be obtained by walking the context
   * tree using {@link #children()}.
   *
   * @throws UnsupportedOperationException if this is not a top-level context.
   * @see #children()
   */
  public abstract List leaves() throws UnsupportedOperationException;

  /**
   * Returns the context's children iff this context is a composite context otherwise null
   * .
   */
  public abstract List children();
}