Fieldable.cs

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/* 
 * 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
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using System;
using System.IO;
using TokenStream = Lucene.Net.Analysis.TokenStream;
using FieldInvertState = Lucene.Net.Index.FieldInvertState;

namespace Lucene.Net.Documents
{
    /// <summary> Synonymous with <see cref="Field" />.
    /// 
    /// <p/><bold>WARNING</bold>: This interface may change within minor versions, despite Lucene's backward compatibility requirements.
    /// This means new methods may be added from version to version.  This change only affects the Fieldable API; other backwards
    /// compatibility promises remain intact. For example, Lucene can still
    /// read and write indices created within the same major version.
    /// <p/>
    /// 
    /// 
    /// </summary>
    public interface IFieldable
    {
        /// <summary>Gets or sets the boost factor for hits for this field.  This value will be
        /// multiplied into the score of all hits on this this field of this
        /// document.
        /// 
        /// <p/>The boost is multiplied by <see cref="Lucene.Net.Documents.Document.Boost" /> of the document
        /// containing this field.  If a document has multiple fields with the same
        /// name, all such values are multiplied together.  This product is then
        /// used to compute the norm factor for the field.  By
        /// default, in the <see cref="Lucene.Net.Search.Similarity.ComputeNorm(String,Lucene.Net.Index.FieldInvertState)"/>
        /// method, the boost value is multiplied
        /// by the <see cref="Lucene.Net.Search.Similarity.LengthNorm(String,int)"/>
        /// and then rounded by <see cref="Lucene.Net.Search.Similarity.EncodeNorm(float)" /> before it is stored in the
        /// index.  One should attempt to ensure that this product does not overflow
        /// the range of that encoding.
        /// 
        /// <p/>The default value is 1.0.
        /// 
        /// <p/>Note: this value is not stored directly with the document in the index.
        /// Documents returned from <see cref="Lucene.Net.Index.IndexReader.Document(int)" /> and
        /// <see cref="Lucene.Net.Search.Searcher.Doc(int)" /> may thus not have the same value present as when
        /// this field was indexed.
        /// 
        /// </summary>
        /// <seealso cref="Lucene.Net.Documents.Document.Boost">
        /// </seealso>
        /// <seealso cref="Lucene.Net.Search.Similarity.ComputeNorm(String, FieldInvertState)">
        /// </seealso>
        /// <seealso cref="Lucene.Net.Search.Similarity.EncodeNorm(float)">
        /// </seealso>
        float Boost { get; set; }

        /// <summary>Returns the name of the field as an interned string.
        /// For example "date", "title", "body", ...
        /// </summary>
        string Name { get; }

        /// <summary>The value of the field as a String, or null.
        /// <p/>
        /// For indexing, if isStored()==true, the stringValue() will be used as the stored field value
        /// unless isBinary()==true, in which case GetBinaryValue() will be used.
        /// 
        /// If isIndexed()==true and isTokenized()==false, this String value will be indexed as a single token.
        /// If isIndexed()==true and isTokenized()==true, then tokenStreamValue() will be used to generate indexed tokens if not null,
        /// else readerValue() will be used to generate indexed tokens if not null, else stringValue() will be used to generate tokens.
        /// </summary>
        string StringValue { get; }

        /// <summary>The value of the field as a Reader, which can be used at index time to generate indexed tokens.</summary>
        /// <seealso cref="StringValue()">
        /// </seealso>
        TextReader ReaderValue { get; }

        /// <summary>The TokenStream for this field to be used when indexing, or null.</summary>
        /// <seealso cref="StringValue()">
        /// </seealso>
        TokenStream TokenStreamValue { get; }

        /// <summary>True if the value of the field is to be stored in the index for return
        /// with search hits. 
        /// </summary>
        bool IsStored { get; }

        /// <summary>True if the value of the field is to be indexed, so that it may be
        /// searched on. 
        /// </summary>
        bool IsIndexed { get; }

        /// <summary>True if the value of the field should be tokenized as text prior to
        /// indexing.  Un-tokenized fields are indexed as a single word and may not be
        /// Reader-valued. 
        /// </summary>
        bool IsTokenized { get; }

        /// <summary>True if the term or terms used to index this field are stored as a term
        /// vector, available from <see cref="Lucene.Net.Index.IndexReader.GetTermFreqVector(int,String)" />.
        /// These methods do not provide access to the original content of the field,
        /// only to terms used to index it. If the original content must be
        /// preserved, use the <c>stored</c> attribute instead.
        /// 
        /// </summary>
        /// <seealso cref="Lucene.Net.Index.IndexReader.GetTermFreqVector(int, String)">
        /// </seealso>
        bool IsTermVectorStored { get; }

        /// <summary> True if terms are stored as term vector together with their offsets 
        /// (start and end positon in source text).
        /// </summary>
        bool IsStoreOffsetWithTermVector { get; }

        /// <summary> True if terms are stored as term vector together with their token positions.</summary>
        bool IsStorePositionWithTermVector { get; }

        /// <summary>True if the value of the field is stored as binary </summary>
        bool IsBinary { get; }

        /// <summary>
        /// True if norms are omitted for this indexed field.
        /// <para>
        /// Expert:
        /// If set, omit normalization factors associated with this indexed field.
        /// This effectively disables indexing boosts and length normalization for this field.
        /// </para>
        /// </summary>
        bool OmitNorms { get; set; }


        /// <summary> Indicates whether a Field is Lazy or not.  The semantics of Lazy loading are such that if a Field is lazily loaded, retrieving
        /// it's values via <see cref="StringValue()" /> or <see cref="GetBinaryValue()" /> is only valid as long as the <see cref="Lucene.Net.Index.IndexReader" /> that
        /// retrieved the <see cref="Document" /> is still open.
        /// 
        /// </summary>
        /// <value> true if this field can be loaded lazily </value>
        bool IsLazy { get; }

        /// <summary> Returns offset into byte[] segment that is used as value, if Field is not binary
        /// returned value is undefined
        /// </summary>
        /// <value> index of the first character in byte[] segment that represents this Field value </value>
        int BinaryOffset { get; }

        /// <summary> Returns length of byte[] segment that is used as value, if Field is not binary
        /// returned value is undefined
        /// </summary>
        /// <value> length of byte[] segment that represents this Field value </value>
        int BinaryLength { get; }

        /// <summary> Return the raw byte[] for the binary field.  Note that
        /// you must also call <see cref="BinaryLength" /> and <see cref="BinaryOffset" />
        /// to know which range of bytes in this
        /// returned array belong to the field.
        /// </summary>
        /// <returns> reference to the Field value as byte[]. </returns>
        byte[] GetBinaryValue();

        /// <summary> Return the raw byte[] for the binary field.  Note that
        /// you must also call <see cref="BinaryLength" /> and <see cref="BinaryOffset" />
        /// to know which range of bytes in this
        /// returned array belong to the field.<p/>
        /// About reuse: if you pass in the result byte[] and it is
        /// used, likely the underlying implementation will hold
        /// onto this byte[] and return it in future calls to
        /// <see cref="GetBinaryValue()" /> or <see cref="GetBinaryValue()" />.
        /// So if you subsequently re-use the same byte[] elsewhere
        /// it will alter this Fieldable's value.
        /// </summary>
        /// <param name="result"> User defined buffer that will be used if
        /// possible.  If this is null or not large enough, a new
        /// buffer is allocated
        /// </param>
        /// <returns> reference to the Field value as byte[].
        /// </returns>
        byte[] GetBinaryValue(byte[] result);

        /// Expert:
        /// <para>
        /// If set, omit term freq, positions and payloads from
        /// postings for this field.
        /// </para>
        /// <para>
        /// <b>NOTE</b>: While this option reduces storage space
        /// required in the index, it also means any query
        /// requiring positional information, such as
        /// <see cref="Lucene.Net.Search.PhraseQuery"/> or 
        /// <see cref="Lucene.Net.Search.Spans.SpanQuery"/> 
        /// subclasses will silently fail to find results.
        /// </para>
        bool OmitTermFreqAndPositions { set; get; }
    }
}