src/Lucene.Net.Core/Index/AtomicReader.cs

using System.Diagnostics;

namespace Lucene.Net.Index
{
    /*
     * 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.
     */

    // javadocs
    using Bits = Lucene.Net.Util.Bits;

    /// <summary>
    /// {@code AtomicReader} is an abstract class, providing an interface for accessing an
    /// index.  Search of an index is done entirely through this abstract interface,
    /// so that any subclass which implements it is searchable. IndexReaders implemented
    /// by this subclass do not consist of several sub-readers,
    /// they are atomic. They support retrieval of stored fields, doc values, terms,
    /// and postings.
    ///
    /// <p>For efficiency, in this API documents are often referred to via
    /// <i>document numbers</i>, non-negative integers which each name a unique
    /// document in the index.  These document numbers are ephemeral -- they may change
    /// as documents are added to and deleted from an index.  Clients should thus not
    /// rely on a given document having the same number between sessions.
    ///
    /// <p>
    /// <a name="thread-safety"></a><p><b>NOTE</b>: {@link
    /// IndexReader} instances are completely thread
    /// safe, meaning multiple threads can call any of its methods,
    /// concurrently.  If your application requires external
    /// synchronization, you should <b>not</b> synchronize on the
    /// <code>IndexReader</code> instance; use your own
    /// (non-Lucene) objects instead.
    /// </summary>
    public abstract class AtomicReader : IndexReader
    {
        private bool InstanceFieldsInitialized = false;

        private void InitializeInstanceFields()
        {
            ReaderContext = new AtomicReaderContext(this);
        }

        private AtomicReaderContext ReaderContext;

        /// <summary>
        /// Sole constructor. (For invocation by subclass
        ///  constructors, typically implicit.)
        /// </summary>
        protected internal AtomicReader()
            : base()
        {
            if (!InstanceFieldsInitialized)
            {
                InitializeInstanceFields();
                InstanceFieldsInitialized = true;
            }
        }

        public sealed override IndexReaderContext Context
        {
            get
            {
                EnsureOpen();
                return ReaderContext;
            }
        }

        public AtomicReaderContext AtomicContext
        {
            get
            {
                EnsureOpen();
                return ReaderContext;
            }
        }

        /// <summary>
        /// Returns true if there are norms stored for this field. </summary>
        /// @deprecated (4.0) use <seealso cref="#getFieldInfos()"/> and check <seealso cref="FieldInfo#hasNorms()"/>
        ///                   for the field instead.
        public bool HasNorms(string field)
        {
            EnsureOpen();
            // note: using normValues(field) != null would potentially cause i/o
            FieldInfo fi = FieldInfos.FieldInfo(field);
            return fi != null && fi.HasNorms();
        }

        /// <summary>
        /// Returns <seealso cref="Fields"/> for this reader.
        /// this method may return null if the reader has no
        /// postings.
        /// </summary>
        public abstract Fields Fields { get; }

        public override sealed int DocFreq(Term term)
        {
            Fields fields = Fields;
            if (fields == null)
            {
                return 0;
            }
            Terms terms = fields.Terms(term.Field);
            if (terms == null)
            {
                return 0;
            }
            TermsEnum termsEnum = terms.Iterator(null);
            if (termsEnum.SeekExact(term.Bytes))
            {
                return termsEnum.DocFreq();
            }
            else
            {
                return 0;
            }
        }

        /// <summary>
        /// Returns the number of documents containing the term
        /// <code>t</code>.  this method returns 0 if the term or
        /// field does not exists.  this method does not take into
        /// account deleted documents that have not yet been merged
        /// away.
        /// </summary>
        public override sealed long TotalTermFreq(Term term)
        {
            Fields fields = Fields;
            if (fields == null)
            {
                return 0;
            }
            Terms terms = fields.Terms(term.Field);
            if (terms == null)
            {
                return 0;
            }
            TermsEnum termsEnum = terms.Iterator(null);
            if (termsEnum.SeekExact(term.Bytes))
            {
                return termsEnum.TotalTermFreq();
            }
            else
            {
                return 0;
            }
        }

        public override sealed long GetSumDocFreq(string field)
        {
            Terms terms = Terms(field);
            if (terms == null)
            {
                return 0;
            }
            return terms.SumDocFreq;
        }

        public override sealed int GetDocCount(string field)
        {
            Terms terms = Terms(field);
            if (terms == null)
            {
                return 0;
            }
            return terms.DocCount;
        }

        public override sealed long GetSumTotalTermFreq(string field)
        {
            Terms terms = Terms(field);
            if (terms == null)
            {
                return 0;
            }
            return terms.SumTotalTermFreq;
        }

        /// <summary>
        /// this may return null if the field does not exist. </summary>
        public Terms Terms(string field)
        {
            Fields fields = Fields;
            if (fields == null)
            {
                return null;
            }
            return fields.Terms(field);
        }

        /// <summary>
        /// Returns <seealso cref="DocsEnum"/> for the specified term.
        ///  this will return null if either the field or
        ///  term does not exist. </summary>
        ///  <seealso cref= TermsEnum#docs(Bits, DocsEnum)  </seealso>
        public DocsEnum TermDocsEnum(Term term)
        {
            Debug.Assert(term.Field != null);
            Debug.Assert(term.Bytes != null);
            Fields fields = Fields;
            if (fields != null)
            {
                Terms terms = fields.Terms(term.Field);
                if (terms != null)
                {
                    TermsEnum termsEnum = terms.Iterator(null);
                    if (termsEnum.SeekExact(term.Bytes))
                    {
                        return termsEnum.Docs(LiveDocs, null);
                    }
                }
            }
            return null;
        }

        /// <summary>
        /// Returns <seealso cref="DocsAndPositionsEnum"/> for the specified
        ///  term.  this will return null if the
        ///  field or term does not exist or positions weren't indexed. </summary>
        ///  <seealso cref= TermsEnum#docsAndPositions(Bits, DocsAndPositionsEnum)  </seealso>
        public DocsAndPositionsEnum TermPositionsEnum(Term term)
        {
            Debug.Assert(term.Field != null);
            Debug.Assert(term.Bytes != null);
            Fields fields = Fields;
            if (fields != null)
            {
                Terms terms = fields.Terms(term.Field);
                if (terms != null)
                {
                    TermsEnum termsEnum = terms.Iterator(null);
                    if (termsEnum.SeekExact(term.Bytes))
                    {
                        return termsEnum.DocsAndPositions(LiveDocs, null);
                    }
                }
            }
            return null;
        }

        /// <summary>
        /// Returns <seealso cref="NumericDocValues"/> for this field, or
        ///  null if no <seealso cref="NumericDocValues"/> were indexed for
        ///  this field.  The returned instance should only be
        ///  used by a single thread.
        /// </summary>
        public abstract NumericDocValues GetNumericDocValues(string field);

        /// <summary>
        /// Returns <seealso cref="BinaryDocValues"/> for this field, or
        ///  null if no <seealso cref="BinaryDocValues"/> were indexed for
        ///  this field.  The returned instance should only be
        ///  used by a single thread.
        /// </summary>
        public abstract BinaryDocValues GetBinaryDocValues(string field);

        /// <summary>
        /// Returns <seealso cref="SortedDocValues"/> for this field, or
        ///  null if no <seealso cref="SortedDocValues"/> were indexed for
        ///  this field.  The returned instance should only be
        ///  used by a single thread.
        /// </summary>
        public abstract SortedDocValues GetSortedDocValues(string field);

        /// <summary>
        /// Returns <seealso cref="SortedSetDocValues"/> for this field, or
        ///  null if no <seealso cref="SortedSetDocValues"/> were indexed for
        ///  this field.  The returned instance should only be
        ///  used by a single thread.
        /// </summary>
        public abstract SortedSetDocValues GetSortedSetDocValues(string field);

        /// <summary>
        /// Returns a <seealso cref="Bits"/> at the size of <code>reader.maxDoc()</code>,
        ///  with turned on bits for each docid that does have a value for this field,
        ///  or null if no DocValues were indexed for this field. The
        ///  returned instance should only be used by a single thread
        /// </summary>
        public abstract Bits GetDocsWithField(string field);

        /// <summary>
        /// Returns <seealso cref="NumericDocValues"/> representing norms
        ///  for this field, or null if no <seealso cref="NumericDocValues"/>
        ///  were indexed. The returned instance should only be
        ///  used by a single thread.
        /// </summary>
        public abstract NumericDocValues GetNormValues(string field);

        /// <summary>
        /// Get the <seealso cref="FieldInfos"/> describing all fields in
        /// this reader.
        /// @lucene.experimental
        /// </summary>
        public abstract FieldInfos FieldInfos { get; }

        /// <summary>
        /// Returns the <seealso cref="Bits"/> representing live (not
        ///  deleted) docs.  A set bit indicates the doc ID has not
        ///  been deleted.  If this method returns null it means
        ///  there are no deleted documents (all documents are
        ///  live).
        ///
        ///  The returned instance has been safely published for
        ///  use by multiple threads without additional
        ///  synchronization.
        /// </summary>
        public abstract Bits LiveDocs { get; }

        /// <summary>
        /// Checks consistency of this reader.
        /// <p>
        /// Note that this may be costly in terms of I/O, e.g.
        /// may involve computing a checksum value against large data files.
        /// @lucene.internal
        /// </summary>
        public abstract void CheckIntegrity();
    }
}