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From: synhershko@apache.org
To: commits@lucenenet.apache.org
Date: Sun, 23 Aug 2015 22:34:11 -0000
Message-Id: <6f21b9fa95264a82a5ff3499a9135788@git.apache.org>
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Subject: [12/17] lucenenet git commit: Lucene.Net.Join tests now passing

http://git-wip-us.apache.org/repos/asf/lucenenet/blob/4820f236/src/Lucene.Net.Grouping/TopGroups.cs
----------------------------------------------------------------------
diff --git a/src/Lucene.Net.Grouping/TopGroups.cs b/src/Lucene.Net.Grouping/TopGroups.cs
new file mode 100644
index 0000000..017c975
--- /dev/null
+++ b/src/Lucene.Net.Grouping/TopGroups.cs
@@ -0,0 +1,249 @@
+using System;
+using Lucene.Net.Search;
+
+namespace Lucene.Net.Grouping
+{
+    /*
+	 * 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.
+	 */
+
+    /// <summary>
+    /// Represents result returned by a grouping search.
+    /// 
+    /// @lucene.experimental 
+    /// </summary>
+    public class TopGroups<TGroupValueType>
+    {
+        /// <summary>
+        /// Number of documents matching the search </summary>
+        public readonly int TotalHitCount;
+
+        /// <summary>
+        /// Number of documents grouped into the topN groups </summary>
+        public readonly int TotalGroupedHitCount;
+
+        /// <summary>
+        /// The total number of unique groups. If <code>null</code> this value is not computed. </summary>
+        public readonly int? TotalGroupCount;
+
+        /// <summary>
+        /// Group results in groupSort order </summary>
+        public readonly GroupDocs<TGroupValueType>[] Groups;
+
+        /// <summary>
+        /// How groups are sorted against each other </summary>
+        public readonly SortField[] GroupSort;
+
+        /// <summary>
+        /// How docs are sorted within each group </summary>
+        public readonly SortField[] WithinGroupSort;
+
+        /// <summary>
+        /// Highest score across all hits, or
+        ///  <code>Float.NaN</code> if scores were not computed. 
+        /// </summary>
+        public readonly float MaxScore;
+
+        public TopGroups(SortField[] groupSort, SortField[] withinGroupSort, int totalHitCount, int totalGroupedHitCount, GroupDocs<TGroupValueType>[] groups, float maxScore)
+        {
+            GroupSort = groupSort;
+            WithinGroupSort = withinGroupSort;
+            TotalHitCount = totalHitCount;
+            TotalGroupedHitCount = totalGroupedHitCount;
+            Groups = groups;
+            TotalGroupCount = null;
+            MaxScore = maxScore;
+        }
+
+        public TopGroups(TopGroups<TGroupValueType> oldTopGroups, int? totalGroupCount)
+        {
+            GroupSort = oldTopGroups.GroupSort;
+            WithinGroupSort = oldTopGroups.WithinGroupSort;
+            TotalHitCount = oldTopGroups.TotalHitCount;
+            TotalGroupedHitCount = oldTopGroups.TotalGroupedHitCount;
+            Groups = oldTopGroups.Groups;
+            MaxScore = oldTopGroups.MaxScore;
+            TotalGroupCount = totalGroupCount;
+        }
+
+        /// <summary>
+        /// How the GroupDocs score (if any) should be merged. </summary>
+        public enum ScoreMergeMode
+        {
+            /// <summary>
+            /// Set score to Float.NaN
+            /// </summary>
+            None,
+
+            /// <summary>
+            /// Sum score across all shards for this group.
+            /// </summary>
+            Total,
+
+            /// <summary>
+            /// Avg score across all shards for this group.
+            /// </summary>
+            Avg,
+        }
+
+        /// <summary>
+        /// Merges an array of TopGroups, for example obtained from the second-pass 
+        /// collector across multiple shards. Each TopGroups must have been sorted by the
+        /// same groupSort and docSort, and the top groups passed to all second-pass 
+        /// collectors must be the same.
+        /// 
+        /// <b>NOTE</b>: We can't always compute an exact totalGroupCount.
+        /// Documents belonging to a group may occur on more than
+        /// one shard and thus the merged totalGroupCount can be
+        /// higher than the actual totalGroupCount. In this case the
+        /// totalGroupCount represents a upper bound. If the documents
+        /// of one group do only reside in one shard then the
+        /// totalGroupCount is exact.
+        /// 
+        /// <b>NOTE</b>: the topDocs in each GroupDocs is actually
+        /// an instance of TopDocsAndShards
+        /// </summary>
+        public static TopGroups<T> Merge<T>(TopGroups<T>[] shardGroups, Sort groupSort, Sort docSort, int docOffset, int docTopN, ScoreMergeMode scoreMergeMode)
+        {
+            //System.out.println("TopGroups.merge");
+
+            if (shardGroups.Length == 0)
+            {
+                return null;
+            }
+
+            int totalHitCount = 0;
+            int totalGroupedHitCount = 0;
+            // Optionally merge the totalGroupCount.
+            int? totalGroupCount = null;
+
+            int numGroups = shardGroups[0].Groups.Length;
+            foreach (var shard in shardGroups)
+            {
+                if (numGroups != shard.Groups.Length)
+                {
+                    throw new ArgumentException("number of groups differs across shards; you must pass same top groups to all shards' second-pass collector");
+                }
+                totalHitCount += shard.TotalHitCount;
+                totalGroupedHitCount += shard.TotalGroupedHitCount;
+                if (shard.TotalGroupCount != null)
+                {
+                    if (totalGroupCount == null)
+                    {
+                        totalGroupCount = 0;
+                    }
+
+                    totalGroupCount += shard.TotalGroupCount;
+                }
+            }
+            
+            var mergedGroupDocs = new GroupDocs<T>[numGroups];
+
+            TopDocs[] shardTopDocs = new TopDocs[shardGroups.Length];
+            float totalMaxScore = float.MinValue;
+
+            for (int groupIDX = 0; groupIDX < numGroups; groupIDX++)
+            {
+                T groupValue = shardGroups[0].Groups[groupIDX].GroupValue;
+                //System.out.println("  merge groupValue=" + groupValue + " sortValues=" + Arrays.toString(shardGroups[0].groups[groupIDX].groupSortValues));
+                float maxScore = float.MinValue;
+                int totalHits = 0;
+                double scoreSum = 0.0;
+                for (int shardIdx = 0; shardIdx < shardGroups.Length; shardIdx++)
+                {
+                    //System.out.println("    shard=" + shardIDX);
+                    TopGroups<T> shard = shardGroups[shardIdx];
+                    var shardGroupDocs = shard.Groups[groupIDX];
+                    if (groupValue == null)
+                    {
+                        if (shardGroupDocs.GroupValue != null)
+                        {
+                            throw new ArgumentException("group values differ across shards; you must pass same top groups to all shards' second-pass collector");
+                        }
+                    }
+                    else if (!groupValue.Equals(shardGroupDocs.GroupValue))
+                    {
+                        throw new ArgumentException("group values differ across shards; you must pass same top groups to all shards' second-pass collector");
+                    }
+
+                    /*
+                    for(ScoreDoc sd : shardGroupDocs.scoreDocs) {
+                      System.out.println("      doc=" + sd.doc);
+                    }
+                    */
+
+                    shardTopDocs[shardIdx] = new TopDocs(shardGroupDocs.TotalHits, shardGroupDocs.ScoreDocs, shardGroupDocs.MaxScore);
+                    maxScore = Math.Max(maxScore, shardGroupDocs.MaxScore);
+                    totalHits += shardGroupDocs.TotalHits;
+                    scoreSum += shardGroupDocs.Score;
+                }
+
+                TopDocs mergedTopDocs = TopDocs.Merge(docSort, docOffset + docTopN, shardTopDocs);
+
+                // Slice;
+                ScoreDoc[] mergedScoreDocs;
+                if (docOffset == 0)
+                {
+                    mergedScoreDocs = mergedTopDocs.ScoreDocs;
+                }
+                else if (docOffset >= mergedTopDocs.ScoreDocs.Length)
+                {
+                    mergedScoreDocs = new ScoreDoc[0];
+                }
+                else
+                {
+                    mergedScoreDocs = new ScoreDoc[mergedTopDocs.ScoreDocs.Length - docOffset];
+                    Array.Copy(mergedTopDocs.ScoreDocs, docOffset, mergedScoreDocs, 0, mergedTopDocs.ScoreDocs.Length - docOffset);
+                }
+
+                float groupScore;
+                switch (scoreMergeMode)
+                {
+                    case ScoreMergeMode.None:
+                        groupScore = float.NaN;
+                        break;
+                    case ScoreMergeMode.Avg:
+                        if (totalHits > 0)
+                        {
+                            groupScore = (float)(scoreSum / totalHits);
+                        }
+                        else
+                        {
+                            groupScore = float.NaN;
+                        }
+                        break;
+                    case ScoreMergeMode.Total:
+                        groupScore = (float)scoreSum;
+                        break;
+                    default:
+                        throw new ArgumentException("can't handle ScoreMergeMode " + scoreMergeMode);
+                }
+
+                //System.out.println("SHARDS=" + Arrays.toString(mergedTopDocs.shardIndex));
+                mergedGroupDocs[groupIDX] = new GroupDocs<T>(groupScore, maxScore, totalHits, mergedScoreDocs, groupValue, shardGroups[0].Groups[groupIDX].GroupSortValues);
+                totalMaxScore = Math.Max(totalMaxScore, maxScore);
+            }
+
+            if (totalGroupCount != null)
+            {
+                var result = new TopGroups<T>(groupSort.GetSort(), docSort == null ? null : docSort.GetSort(), totalHitCount, totalGroupedHitCount, mergedGroupDocs, totalMaxScore);
+                return new TopGroups<T>(result, totalGroupCount);
+            }
+
+            return new TopGroups<T>(groupSort.GetSort(), docSort == null ? null : docSort.GetSort(), totalHitCount, totalGroupedHitCount, mergedGroupDocs, totalMaxScore);
+        }
+    }
+}
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/lucenenet/blob/4820f236/src/Lucene.Net.Join/FakeScorer.cs
----------------------------------------------------------------------
diff --git a/src/Lucene.Net.Join/FakeScorer.cs b/src/Lucene.Net.Join/FakeScorer.cs
new file mode 100644
index 0000000..42bf91b
--- /dev/null
+++ b/src/Lucene.Net.Join/FakeScorer.cs
@@ -0,0 +1,76 @@
+using System;
+using System.Collections.Generic;
+using Lucene.Net.Search;
+
+namespace Lucene.Net.Join
+{
+    /*
+	 * 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.
+	 */
+
+    /// <summary>
+	/// Passed to <see cref="Collector.Scorer"/> during join collection.
+	/// </summary>
+    internal sealed class FakeScorer : Scorer
+    {
+        internal float _score;
+        internal int doc = -1;
+
+        public FakeScorer() : base(null)
+        {
+        }
+
+        public override int DocID()
+        {
+            return doc;
+        }
+
+        public override int NextDoc()
+        {
+            throw new NotSupportedException("FakeScorer doesn't support NextDoc()");
+        }
+
+        public override int Advance(int target)
+        {
+            throw new NotSupportedException("FakeScorer doesn't support Advance(int)");
+        }
+
+        public override long Cost()
+        {
+            return 1;
+        }
+
+        public override int Freq()
+        {
+            throw new NotSupportedException("FakeScorer doesn't support Freq()");
+        }
+
+        public override float Score()
+        {
+            return _score;
+        }
+
+        public override Weight Weight
+        {
+            get { throw new NotSupportedException(); }
+        }
+
+        public override ICollection<ChildScorer> Children
+        {
+            get { throw new NotSupportedException(); }
+        }
+    }
+}
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/lucenenet/blob/4820f236/src/Lucene.Net.Join/FixedBitSetCachingWrapperFilter.cs
----------------------------------------------------------------------
diff --git a/src/Lucene.Net.Join/FixedBitSetCachingWrapperFilter.cs b/src/Lucene.Net.Join/FixedBitSetCachingWrapperFilter.cs
new file mode 100644
index 0000000..da8b0b8
--- /dev/null
+++ b/src/Lucene.Net.Join/FixedBitSetCachingWrapperFilter.cs
@@ -0,0 +1,62 @@
+using Lucene.Net.Index;
+using Lucene.Net.Search;
+using Lucene.Net.Util;
+
+namespace Lucene.Net.Join
+{
+    /*
+	 * 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.
+	 */
+
+    /// <summary>
+	/// A <see cref="CachingWrapperFilter"/> that caches sets using a <see cref="FixedBitSet"/>,
+	/// as required for joins. 
+	/// </summary>
+    public sealed class FixedBitSetCachingWrapperFilter : CachingWrapperFilter
+    {
+        /// <summary>
+        /// Sole constructor, see <see cref="CachingWrapperFilter"/>.
+        /// </summary>
+        public FixedBitSetCachingWrapperFilter(Filter filter) : base(filter)
+        {
+        }
+
+        protected override DocIdSet DocIdSetToCache(DocIdSet docIdSet, AtomicReader reader)
+        {
+            if (docIdSet == null)
+            {
+                return EMPTY_DOCIDSET;
+            }
+
+            if (docIdSet is FixedBitSet)
+            {
+                // this is different from CachingWrapperFilter: even when the DocIdSet is
+                // cacheable, we convert it to a FixedBitSet since we require all the
+                // cached filters to be FixedBitSets
+                return docIdSet;
+            }
+
+            DocIdSetIterator it = docIdSet.GetIterator();
+            if (it == null)
+            {
+                return EMPTY_DOCIDSET;
+            }
+            FixedBitSet copy = new FixedBitSet(reader.MaxDoc);
+            copy.Or(it);
+            return copy;
+        }
+    }
+}
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/lucenenet/blob/4820f236/src/Lucene.Net.Join/JoinUtil.cs
----------------------------------------------------------------------
diff --git a/src/Lucene.Net.Join/JoinUtil.cs b/src/Lucene.Net.Join/JoinUtil.cs
new file mode 100644
index 0000000..726731e
--- /dev/null
+++ b/src/Lucene.Net.Join/JoinUtil.cs
@@ -0,0 +1,80 @@
+using System.IO;
+using Lucene.Net.Search;
+
+namespace Lucene.Net.Join
+{
+    /*
+	 * 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.
+	 */
+
+
+    /// <summary>
+	/// Utility for query time joining using TermsQuery and TermsCollector.
+	/// 
+	/// @lucene.experimental
+	/// </summary>
+    public sealed class JoinUtil
+    {
+        // No instances allowed
+        private JoinUtil()
+        {
+        }
+
+        /// <summary>
+        /// Method for query time joining.
+        /// <p/>
+        /// Execute the returned query with a <seealso cref="IndexSearcher"/> to retrieve all documents that have the same terms in the
+        /// to field that match with documents matching the specified fromQuery and have the same terms in the from field.
+        /// <p/>
+        /// In the case a single document relates to more than one document the <code>multipleValuesPerDocument</code> option
+        /// should be set to true. When the <code>multipleValuesPerDocument</code> is set to <code>true</code> only the
+        /// the score from the first encountered join value originating from the 'from' side is mapped into the 'to' side.
+        /// Even in the case when a second join value related to a specific document yields a higher score. Obviously this
+        /// doesn't apply in the case that <seealso cref="ScoreMode.None"/> is used, since no scores are computed at all.
+        /// </p>
+        /// Memory considerations: During joining all unique join values are kept in memory. On top of that when the scoreMode
+        /// isn't set to <seealso cref="ScoreMode.None"/> a float value per unique join value is kept in memory for computing scores.
+        /// When scoreMode is set to <seealso cref="ScoreMode.Avg"/> also an additional integer value is kept in memory per unique
+        /// join value.
+        /// </summary>
+        /// <param name="fromField">                 The from field to join from </param>
+        /// <param name="multipleValuesPerDocument"> Whether the from field has multiple terms per document </param>
+        /// <param name="toField">                   The to field to join to </param>
+        /// <param name="fromQuery">                 The query to match documents on the from side </param>
+        /// <param name="fromSearcher">              The searcher that executed the specified fromQuery </param>
+        /// <param name="scoreMode">                 Instructs how scores from the fromQuery are mapped to the returned query </param>
+        /// <returns>A <see cref="Query"/> instance that can be used to join documents based on the terms in the from and to field</returns>
+        /// <exception cref="IOException"> If I/O related errors occur </exception>
+        public static Query CreateJoinQuery(string fromField, bool multipleValuesPerDocument, string toField, Query fromQuery, IndexSearcher fromSearcher, ScoreMode scoreMode)
+        {
+            switch (scoreMode)
+            {
+                case ScoreMode.None:
+                    TermsCollector termsCollector = TermsCollector.Create(fromField, multipleValuesPerDocument);
+                    fromSearcher.Search(fromQuery, termsCollector);
+                    return new TermsQuery(toField, fromQuery, termsCollector.CollectorTerms);
+                case ScoreMode.Total:
+                case ScoreMode.Max:
+                case ScoreMode.Avg:
+                    TermsWithScoreCollector termsWithScoreCollector = TermsWithScoreCollector.Create(fromField, multipleValuesPerDocument, scoreMode);
+                    fromSearcher.Search(fromQuery, termsWithScoreCollector);
+                    return new TermsIncludingScoreQuery(toField, multipleValuesPerDocument, termsWithScoreCollector.CollectedTerms, termsWithScoreCollector.ScoresPerTerm, fromQuery);
+                default:
+                    throw new System.ArgumentException(string.Format("Score mode {0} isn't supported.", scoreMode));
+            }
+        }
+    }
+}
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/lucenenet/blob/4820f236/src/Lucene.Net.Join/Lucene.Net.Join.csproj
----------------------------------------------------------------------
diff --git a/src/Lucene.Net.Join/Lucene.Net.Join.csproj b/src/Lucene.Net.Join/Lucene.Net.Join.csproj
new file mode 100644
index 0000000..72bda4a
--- /dev/null
+++ b/src/Lucene.Net.Join/Lucene.Net.Join.csproj
@@ -0,0 +1,76 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <ProjectGuid>{E8A339C7-FCF6-4A72-8586-56D8961D7B99}</ProjectGuid>
+    <OutputType>Library</OutputType>
+    <AppDesignerFolder>Properties</AppDesignerFolder>
+    <RootNamespace>Lucene.Net.Join</RootNamespace>
+    <AssemblyName>Lucene.Net.Join</AssemblyName>
+    <TargetFrameworkVersion>v4.5.1</TargetFrameworkVersion>
+    <FileAlignment>512</FileAlignment>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+    <DebugSymbols>true</DebugSymbols>
+    <DebugType>full</DebugType>
+    <Optimize>false</Optimize>
+    <OutputPath>bin\Debug\</OutputPath>
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+    <DebugType>pdbonly</DebugType>
+    <Optimize>true</Optimize>
+    <OutputPath>bin\Release\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <ItemGroup>
+    <Reference Include="System" />
+    <Reference Include="System.Core" />
+    <Reference Include="System.Xml.Linq" />
+    <Reference Include="System.Data.DataSetExtensions" />
+    <Reference Include="Microsoft.CSharp" />
+    <Reference Include="System.Data" />
+    <Reference Include="System.Net.Http" />
+    <Reference Include="System.Xml" />
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="FakeScorer.cs" />
+    <Compile Include="FixedBitSetCachingWrapperFilter.cs" />
+    <Compile Include="JoinUtil.cs" />
+    <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="ScoreMode.cs" />
+    <Compile Include="TermsCollector.cs" />
+    <Compile Include="TermsIncludingScoreQuery.cs" />
+    <Compile Include="TermsQuery.cs" />
+    <Compile Include="TermsWithScoreCollector.cs" />
+    <Compile Include="ToChildBlockJoinQuery.cs" />
+    <Compile Include="ToParentBlockJoinCollector.cs" />
+    <Compile Include="ToParentBlockJoinFieldComparator.cs" />
+    <Compile Include="ToParentBlockJoinQuery.cs" />
+    <Compile Include="ToParentBlockJoinSortField.cs" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\Lucene.Net.Grouping\Lucene.Net.Grouping.csproj">
+      <Project>{02BAB603-067D-48B1-AEDD-316849652568}</Project>
+      <Name>Lucene.Net.Grouping</Name>
+    </ProjectReference>
+    <ProjectReference Include="..\Lucene.Net.Core\Lucene.Net.csproj">
+      <Project>{5D4AD9BE-1FFB-41AB-9943-25737971BF57}</Project>
+      <Name>Lucene.Net</Name>
+    </ProjectReference>
+  </ItemGroup>
+  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
+  <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
+       Other similar extension points exist, see Microsoft.Common.targets.
+  <Target Name="BeforeBuild">
+  </Target>
+  <Target Name="AfterBuild">
+  </Target>
+  -->
+</Project>
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/lucenenet/blob/4820f236/src/Lucene.Net.Join/Properties/AssemblyInfo.cs
----------------------------------------------------------------------
diff --git a/src/Lucene.Net.Join/Properties/AssemblyInfo.cs b/src/Lucene.Net.Join/Properties/AssemblyInfo.cs
new file mode 100644
index 0000000..2c17c13
--- /dev/null
+++ b/src/Lucene.Net.Join/Properties/AssemblyInfo.cs
@@ -0,0 +1,36 @@
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+// General Information about an assembly is controlled through the following 
+// set of attributes. Change these attribute values to modify the information
+// associated with an assembly.
+[assembly: AssemblyTitle("Lucene.Net.Join")]
+[assembly: AssemblyDescription("")]
+[assembly: AssemblyConfiguration("")]
+[assembly: AssemblyCompany("")]
+[assembly: AssemblyProduct("Lucene.Net.Join")]
+[assembly: AssemblyCopyright("Copyright ©  2015")]
+[assembly: AssemblyTrademark("")]
+[assembly: AssemblyCulture("")]
+
+// Setting ComVisible to false makes the types in this assembly not visible 
+// to COM components.  If you need to access a type in this assembly from 
+// COM, set the ComVisible attribute to true on that type.
+[assembly: ComVisible(false)]
+
+// The following GUID is for the ID of the typelib if this project is exposed to COM
+[assembly: Guid("e8a339c7-fcf6-4a72-8586-56d8961d7b99")]
+
+// Version information for an assembly consists of the following four values:
+//
+//      Major Version
+//      Minor Version 
+//      Build Number
+//      Revision
+//
+// You can specify all the values or you can default the Build and Revision Numbers 
+// by using the '*' as shown below:
+// [assembly: AssemblyVersion("1.0.*")]
+[assembly: AssemblyVersion("1.0.0.0")]
+[assembly: AssemblyFileVersion("1.0.0.0")]

http://git-wip-us.apache.org/repos/asf/lucenenet/blob/4820f236/src/Lucene.Net.Join/ScoreMode.cs
----------------------------------------------------------------------
diff --git a/src/Lucene.Net.Join/ScoreMode.cs b/src/Lucene.Net.Join/ScoreMode.cs
new file mode 100644
index 0000000..a5b91be
--- /dev/null
+++ b/src/Lucene.Net.Join/ScoreMode.cs
@@ -0,0 +1,45 @@
+namespace Lucene.Net.Join
+{
+    /*
+	 * 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.
+	 */
+
+    /// <summary>
+    /// How to aggregate multiple child hit scores into a single parent score.
+    /// </summary>
+    public enum ScoreMode
+    {
+        /// <summary>
+        /// Do no scoring.
+        /// </summary>
+        None,
+
+        /// <summary>
+        /// Parent hit's score is the average of all child scores.
+        /// </summary>
+        Avg,
+
+        /// <summary>
+        /// Parent hit's score is the max of all child scores.
+        /// </summary>
+        Max,
+
+        /// <summary>
+        /// Parent hit's score is the sum of all child scores.
+        /// </summary>
+        Total
+    }
+}
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/lucenenet/blob/4820f236/src/Lucene.Net.Join/TermsCollector.cs
----------------------------------------------------------------------
diff --git a/src/Lucene.Net.Join/TermsCollector.cs b/src/Lucene.Net.Join/TermsCollector.cs
new file mode 100644
index 0000000..2ccf1ed
--- /dev/null
+++ b/src/Lucene.Net.Join/TermsCollector.cs
@@ -0,0 +1,127 @@
+using Lucene.Net.Index;
+using Lucene.Net.Search;
+using Lucene.Net.Util;
+
+namespace Lucene.Net.Join
+{
+    /*
+	 * 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.
+	 */
+
+    /// <summary>
+	/// A collector that collects all terms from a specified field matching the query.
+	/// 
+	/// @lucene.experimental
+	/// </summary>
+    internal abstract class TermsCollector : Collector
+    {
+        private readonly string _field;
+        private readonly BytesRefHash _collectorTerms = new BytesRefHash();
+
+        internal TermsCollector(string field)
+        {
+            _field = field;
+        }
+
+        public BytesRefHash CollectorTerms
+        {
+            get
+            {
+                return _collectorTerms;
+            }
+        }
+        
+        public override Scorer Scorer
+        {
+            set {}
+        }
+
+        public override bool AcceptsDocsOutOfOrder()
+        {
+            return true;
+        }
+
+        /// <summary>
+        /// Chooses the right <see cref="TermsCollector"/> implementation.
+        /// </summary>
+        /// <param name="field">The field to collect terms for.</param>
+        /// <param name="multipleValuesPerDocument">Whether the field to collect terms for has multiple values per document.</param>
+        /// <returns>A <see cref="TermsCollector"/> instance.</returns>
+        internal static TermsCollector Create(string field, bool multipleValuesPerDocument)
+        {
+            return multipleValuesPerDocument ? (TermsCollector) new MV(field) : new SV(field);
+        }
+
+        // impl that works with multiple values per document
+        private class MV : TermsCollector
+        {
+            private readonly BytesRef _scratch = new BytesRef();
+            private SortedSetDocValues _docTermOrds;
+
+            internal MV(string field) : base(field)
+            {
+            }
+            
+            public override void Collect(int doc)
+            {
+                _docTermOrds.Document = doc;
+                long ord;
+                while ((ord = _docTermOrds.NextOrd()) != SortedSetDocValues.NO_MORE_ORDS)
+                {
+                    _docTermOrds.LookupOrd(ord, _scratch);
+                    _collectorTerms.Add(_scratch);
+                }
+            }
+            
+            public override AtomicReaderContext NextReader
+            {
+                set { _docTermOrds = FieldCache.DEFAULT.GetDocTermOrds(value.AtomicReader, _field); }
+            }
+
+            public override bool AcceptsDocsOutOfOrder()
+            {
+                throw new System.NotImplementedException();
+            }
+        }
+
+        // impl that works with single value per document
+        private class SV : TermsCollector
+        {
+            private readonly BytesRef _spare = new BytesRef();
+            private BinaryDocValues _fromDocTerms;
+
+            internal SV(string field) : base(field)
+            {
+            }
+            
+            public override void Collect(int doc)
+            {
+                _fromDocTerms.Get(doc, _spare);
+                _collectorTerms.Add(_spare);
+            }
+            
+            public override AtomicReaderContext NextReader
+            {
+                set { _fromDocTerms = FieldCache.DEFAULT.GetTerms(value.AtomicReader, _field, false); }
+            }
+
+            public override bool AcceptsDocsOutOfOrder()
+            {
+                return base.AcceptsDocsOutOfOrder();
+            }
+        }
+    }
+}
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/lucenenet/blob/4820f236/src/Lucene.Net.Join/TermsIncludingScoreQuery.cs
----------------------------------------------------------------------
diff --git a/src/Lucene.Net.Join/TermsIncludingScoreQuery.cs b/src/Lucene.Net.Join/TermsIncludingScoreQuery.cs
new file mode 100644
index 0000000..9f3befc
--- /dev/null
+++ b/src/Lucene.Net.Join/TermsIncludingScoreQuery.cs
@@ -0,0 +1,472 @@
+using System.Collections.Generic;
+using Lucene.Net.Index;
+using Lucene.Net.Search;
+using Lucene.Net.Util;
+
+namespace Lucene.Net.Join
+{
+    /*
+	 * 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.
+	 */
+     
+    internal class TermsIncludingScoreQuery : Query
+    {
+        private readonly string _field;
+        private readonly bool _multipleValuesPerDocument;
+        private readonly BytesRefHash _terms;
+        private readonly float[] _scores;
+        private readonly int[] _ords;
+        private readonly Query _originalQuery;
+        private readonly Query _unwrittenOriginalQuery;
+
+        internal TermsIncludingScoreQuery(string field, bool multipleValuesPerDocument, BytesRefHash terms,
+            float[] scores, Query originalQuery)
+        {
+            _field = field;
+            _multipleValuesPerDocument = multipleValuesPerDocument;
+            _terms = terms;
+            _scores = scores;
+            _originalQuery = originalQuery;
+            _ords = terms.Sort(BytesRef.UTF8SortedAsUnicodeComparer);
+            _unwrittenOriginalQuery = originalQuery;
+        }
+
+        private TermsIncludingScoreQuery(string field, bool multipleValuesPerDocument, BytesRefHash terms,
+            float[] scores, int[] ords, Query originalQuery, Query unwrittenOriginalQuery)
+        {
+            _field = field;
+            _multipleValuesPerDocument = multipleValuesPerDocument;
+            _terms = terms;
+            _scores = scores;
+            _originalQuery = originalQuery;
+            _ords = ords;
+            _unwrittenOriginalQuery = unwrittenOriginalQuery;
+        }
+
+        public override string ToString(string @string)
+        {
+            return string.Format("TermsIncludingScoreQuery{{field={0};originalQuery={1}}}", _field,
+                _unwrittenOriginalQuery);
+        }
+
+        public override void ExtractTerms(ISet<Term> terms)
+        {
+            _originalQuery.ExtractTerms(terms);
+        }
+
+        public override Query Rewrite(IndexReader reader)
+        {
+            Query originalQueryRewrite = _originalQuery.Rewrite(reader);
+            if (originalQueryRewrite != _originalQuery)
+            {
+                Query rewritten = new TermsIncludingScoreQuery(_field, _multipleValuesPerDocument, _terms, _scores,
+                    _ords, originalQueryRewrite, _originalQuery);
+                rewritten.Boost = Boost;
+                return rewritten;
+            }
+
+            return this;
+        }
+
+        protected bool Equals(TermsIncludingScoreQuery other)
+        {
+            return base.Equals(other) && string.Equals(_field, other._field) &&
+                   Equals(_unwrittenOriginalQuery, other._unwrittenOriginalQuery);
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (ReferenceEquals(null, obj)) return false;
+            if (ReferenceEquals(this, obj)) return true;
+            if (obj.GetType() != GetType()) return false;
+            return Equals((TermsIncludingScoreQuery) obj);
+        }
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                int hashCode = base.GetHashCode();
+                hashCode = (hashCode*397) ^ (_field != null ? _field.GetHashCode() : 0);
+                hashCode = (hashCode*397) ^
+                           (_unwrittenOriginalQuery != null ? _unwrittenOriginalQuery.GetHashCode() : 0);
+                return hashCode;
+            }
+        }
+
+        public override Weight CreateWeight(IndexSearcher searcher)
+        {
+            Weight originalWeight = _originalQuery.CreateWeight(searcher);
+            return new WeightAnonymousInnerClassHelper(this, originalWeight);
+        }
+
+        private class WeightAnonymousInnerClassHelper : Weight
+        {
+            private readonly TermsIncludingScoreQuery outerInstance;
+
+            private Weight originalWeight;
+
+            public WeightAnonymousInnerClassHelper(TermsIncludingScoreQuery outerInstance, Weight originalWeight)
+            {
+                this.outerInstance = outerInstance;
+                this.originalWeight = originalWeight;
+            }
+
+
+            private TermsEnum segmentTermsEnum;
+            
+            public override Explanation Explain(AtomicReaderContext context, int doc)
+            {
+                SVInnerScorer scorer = (SVInnerScorer) BulkScorer(context, false, null);
+                if (scorer != null)
+                {
+                    return scorer.Explain(doc);
+                }
+                return new ComplexExplanation(false, 0.0f, "Not a match");
+            }
+
+            public override bool ScoresDocsOutOfOrder()
+            {
+                // We have optimized impls below if we are allowed
+                // to score out-of-order:
+                return true;
+            }
+
+            public override Query Query
+            {
+                get { return outerInstance; }
+            }
+            
+            public override float ValueForNormalization
+            {
+                get { return originalWeight.ValueForNormalization*outerInstance.Boost*outerInstance.Boost; }
+            }
+
+            public override void Normalize(float norm, float topLevelBoost)
+            {
+                originalWeight.Normalize(norm, topLevelBoost*outerInstance.Boost);
+            }
+            
+            public override Scorer Scorer(AtomicReaderContext context, Bits acceptDocs)
+            {
+                Terms terms = context.AtomicReader.Terms(outerInstance._field);
+                if (terms == null)
+                {
+                    return null;
+                }
+
+                // what is the runtime...seems ok?
+                long cost = context.AtomicReader.MaxDoc * terms.Size();
+
+                segmentTermsEnum = terms.Iterator(segmentTermsEnum);
+                if (outerInstance._multipleValuesPerDocument)
+                {
+                    return new MVInOrderScorer(outerInstance, this, acceptDocs, segmentTermsEnum, context.AtomicReader.MaxDoc, cost);
+                }
+
+                return new SVInOrderScorer(outerInstance, this, acceptDocs, segmentTermsEnum, context.AtomicReader.MaxDoc, cost);
+            }
+            
+            public override BulkScorer BulkScorer(AtomicReaderContext context, bool scoreDocsInOrder, Bits acceptDocs)
+            {
+                if (scoreDocsInOrder)
+                {
+                    return base.BulkScorer(context, scoreDocsInOrder, acceptDocs);
+                }
+
+                Terms terms = context.AtomicReader.Terms(outerInstance._field);
+                if (terms == null)
+                {
+                    return null;
+                }
+                // what is the runtime...seems ok?
+                long cost = context.AtomicReader.MaxDoc * terms.Size();
+
+                segmentTermsEnum = terms.Iterator(segmentTermsEnum);
+                // Optimized impls that take advantage of docs
+                // being allowed to be out of order:
+                if (outerInstance._multipleValuesPerDocument)
+                {
+                    return new MVInnerScorer(outerInstance, this, acceptDocs, segmentTermsEnum, context.AtomicReader.MaxDoc, cost);
+                }
+
+                return new SVInnerScorer(outerInstance, this, acceptDocs, segmentTermsEnum, cost);
+            }
+        }
+
+        // This impl assumes that the 'join' values are used uniquely per doc per field. Used for one to many relations.
+        internal class SVInnerScorer : BulkScorer
+        {
+            private readonly TermsIncludingScoreQuery outerInstance;
+
+            private readonly BytesRef _spare = new BytesRef();
+            private readonly Bits _acceptDocs;
+            private readonly TermsEnum _termsEnum;
+            private readonly long _cost;
+
+            private int _upto;
+            internal DocsEnum DocsEnum;
+            private DocsEnum _reuse;
+            private int _scoreUpto;
+            private int _doc;
+
+            internal SVInnerScorer(TermsIncludingScoreQuery outerInstance, Weight weight, Bits acceptDocs, TermsEnum termsEnum, long cost)
+            {
+                this.outerInstance = outerInstance;
+                _acceptDocs = acceptDocs;
+                _termsEnum = termsEnum;
+                _cost = cost;
+                _doc = -1;
+            }
+            
+            public override bool Score(Collector collector, int max)
+            {
+                FakeScorer fakeScorer = new FakeScorer();
+                collector.Scorer = fakeScorer;
+                if (_doc == -1)
+                {
+                    _doc = NextDocOutOfOrder();
+                }
+                while (_doc < max)
+                {
+                    fakeScorer.doc = _doc;
+                    fakeScorer._score = outerInstance._scores[outerInstance._ords[_scoreUpto]];
+                    collector.Collect(_doc);
+                    _doc = NextDocOutOfOrder();
+                }
+
+                return _doc != DocIdSetIterator.NO_MORE_DOCS;
+            }
+
+            private int NextDocOutOfOrder()
+            {
+                while (true)
+                {
+                    if (DocsEnum != null)
+                    {
+                        int docId = DocsEnumNextDoc();
+                        if (docId == DocIdSetIterator.NO_MORE_DOCS)
+                        {
+                            DocsEnum = null;
+                        }
+                        else
+                        {
+                            return _doc = docId;
+                        }
+                    }
+
+                    if (_upto == outerInstance._terms.Size())
+                    {
+                        return _doc = DocIdSetIterator.NO_MORE_DOCS;
+                    }
+
+                    _scoreUpto = _upto;
+                    if (_termsEnum.SeekExact(outerInstance._terms.Get(outerInstance._ords[_upto++], _spare)))
+                    {
+                        DocsEnum = _reuse = _termsEnum.Docs(_acceptDocs, _reuse, DocsEnum.FLAG_NONE);
+                    }
+                }
+            }
+            
+            protected virtual int DocsEnumNextDoc()
+            {
+                return DocsEnum.NextDoc();
+            }
+            
+            internal Explanation Explain(int target)
+            {
+                int docId;
+                do
+                {
+                    docId = NextDocOutOfOrder();
+                    if (docId < target)
+                    {
+                        int tempDocId = DocsEnum.Advance(target);
+                        if (tempDocId == target)
+                        {
+                            docId = tempDocId;
+                            break;
+                        }
+                    }
+                    else if (docId == target)
+                    {
+                        break;
+                    }
+                    DocsEnum = null; // goto the next ord.
+                } while (docId != DocIdSetIterator.NO_MORE_DOCS);
+
+                return new ComplexExplanation(true, outerInstance._scores[outerInstance._ords[_scoreUpto]],
+                    "Score based on join value " + _termsEnum.Term().Utf8ToString());
+            }
+        }
+
+        // This impl that tracks whether a docid has already been emitted. This check makes sure that docs aren't emitted
+        // twice for different join values. This means that the first encountered join value determines the score of a document
+        // even if other join values yield a higher score.
+        internal class MVInnerScorer : SVInnerScorer
+        {
+            private readonly TermsIncludingScoreQuery outerInstance;
+
+
+            internal readonly FixedBitSet alreadyEmittedDocs;
+
+            internal MVInnerScorer(TermsIncludingScoreQuery outerInstance, Weight weight, Bits acceptDocs,
+                TermsEnum termsEnum, int maxDoc, long cost) : base(outerInstance, weight, acceptDocs, termsEnum, cost)
+            {
+                this.outerInstance = outerInstance;
+                alreadyEmittedDocs = new FixedBitSet(maxDoc);
+            }
+            
+            protected override int DocsEnumNextDoc()
+            {
+                while (true)
+                {
+                    int docId = DocsEnum.NextDoc();
+                    if (docId == DocIdSetIterator.NO_MORE_DOCS)
+                    {
+                        return docId;
+                    }
+                    if (!alreadyEmittedDocs.GetAndSet(docId))
+                    {
+                        return docId; //if it wasn't previously set, return it
+                    }
+                }
+            }
+        }
+
+        internal class SVInOrderScorer : Scorer
+        {
+            private readonly TermsIncludingScoreQuery outerInstance;
+
+
+            internal readonly DocIdSetIterator matchingDocsIterator;
+            internal readonly float[] scores;
+            internal readonly long cost_Renamed;
+
+            internal int currentDoc = -1;
+            
+            internal SVInOrderScorer(TermsIncludingScoreQuery outerInstance, Weight weight, Bits acceptDocs,
+                TermsEnum termsEnum, int maxDoc, long cost) : base(weight)
+            {
+                this.outerInstance = outerInstance;
+                FixedBitSet matchingDocs = new FixedBitSet(maxDoc);
+                scores = new float[maxDoc];
+                FillDocsAndScores(matchingDocs, acceptDocs, termsEnum);
+                matchingDocsIterator = matchingDocs.GetIterator();
+                cost_Renamed = cost;
+            }
+            
+            protected virtual void FillDocsAndScores(FixedBitSet matchingDocs, Bits acceptDocs,
+                TermsEnum termsEnum)
+            {
+                BytesRef spare = new BytesRef();
+                DocsEnum docsEnum = null;
+                for (int i = 0; i < outerInstance._terms.Size(); i++)
+                {
+                    if (termsEnum.SeekExact(outerInstance._terms.Get(outerInstance._ords[i], spare)))
+                    {
+                        docsEnum = termsEnum.Docs(acceptDocs, docsEnum, FLAG_NONE);
+                        float score = outerInstance._scores[outerInstance._ords[i]];
+                        for (int doc = docsEnum.NextDoc();
+                            doc != NO_MORE_DOCS;
+                            doc = docsEnum.NextDoc())
+                        {
+                            matchingDocs.Set(doc);
+                            // In the case the same doc is also related to a another doc, a score might be overwritten. I think this
+                            // can only happen in a many-to-many relation
+                            scores[doc] = score;
+                        }
+                    }
+                }
+            }
+            
+            public override float Score()
+            {
+                return scores[currentDoc];
+            }
+            
+            public override int Freq()
+            {
+                return 1;
+            }
+
+            public override int DocID()
+            {
+                return currentDoc;
+            }
+            
+            public override int NextDoc()
+            {
+                return currentDoc = matchingDocsIterator.NextDoc();
+            }
+            
+            public override int Advance(int target)
+            {
+                return currentDoc = matchingDocsIterator.Advance(target);
+            }
+
+            public override long Cost()
+            {
+                return cost_Renamed;
+            }
+        }
+
+        // This scorer deals with the fact that a document can have more than one score from multiple related documents.
+        internal class MVInOrderScorer : SVInOrderScorer
+        {
+            private readonly TermsIncludingScoreQuery outerInstance;
+
+            
+            internal MVInOrderScorer(TermsIncludingScoreQuery outerInstance, Weight weight, Bits acceptDocs,
+                TermsEnum termsEnum, int maxDoc, long cost)
+                : base(outerInstance, weight, acceptDocs, termsEnum, maxDoc, cost)
+            {
+                this.outerInstance = outerInstance;
+            }
+            
+            protected override void FillDocsAndScores(FixedBitSet matchingDocs, Bits acceptDocs,
+                TermsEnum termsEnum)
+            {
+                BytesRef spare = new BytesRef();
+                DocsEnum docsEnum = null;
+                for (int i = 0; i < outerInstance._terms.Size(); i++)
+                {
+                    if (termsEnum.SeekExact(outerInstance._terms.Get(outerInstance._ords[i], spare)))
+                    {
+                        docsEnum = termsEnum.Docs(acceptDocs, docsEnum, FLAG_NONE);
+                        float score = outerInstance._scores[outerInstance._ords[i]];
+                        for (int doc = docsEnum.NextDoc();
+                            doc != NO_MORE_DOCS;
+                            doc = docsEnum.NextDoc())
+                        {
+                            // I prefer this:
+                            /*if (scores[doc] < score) {
+                              scores[doc] = score;
+                              matchingDocs.set(doc);
+                            }*/
+                            // But this behaves the same as MVInnerScorer and only then the tests will pass:
+                            if (!matchingDocs.Get(doc))
+                            {
+                                scores[doc] = score;
+                                matchingDocs.Set(doc);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/lucenenet/blob/4820f236/src/Lucene.Net.Join/TermsQuery.cs
----------------------------------------------------------------------
diff --git a/src/Lucene.Net.Join/TermsQuery.cs b/src/Lucene.Net.Join/TermsQuery.cs
new file mode 100644
index 0000000..2d5ccf8
--- /dev/null
+++ b/src/Lucene.Net.Join/TermsQuery.cs
@@ -0,0 +1,147 @@
+using System.Collections.Generic;
+using Lucene.Net.Index;
+using Lucene.Net.Search;
+using Lucene.Net.Util;
+
+namespace Lucene.Net.Join
+{
+    /*
+	 * 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.
+	 */
+
+    /// <summary>
+	/// A query that has an array of terms from a specific field. This query will match documents have one or more terms in
+	/// the specified field that match with the terms specified in the array.
+	/// 
+	/// @lucene.experimental
+	/// </summary>
+    internal class TermsQuery : MultiTermQuery
+    {
+        private readonly BytesRefHash _terms;
+        private readonly int[] _ords;
+        private readonly Query _fromQuery; // Used for equals() only
+
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="field">The field that should contain terms that are specified in the previous parameter.</param>
+        /// <param name="fromQuery"></param>
+        /// <param name="terms">The terms that matching documents should have. The terms must be sorted by natural order.</param>
+        internal TermsQuery(string field, Query fromQuery, BytesRefHash terms) : base(field)
+        {
+            _fromQuery = fromQuery;
+            _terms = terms;
+            _ords = terms.Sort(BytesRef.UTF8SortedAsUnicodeComparer);
+        }
+
+        public override TermsEnum GetTermsEnum(Terms terms, AttributeSource atts)
+        {
+            if (_terms.Size() == 0)
+            {
+                return TermsEnum.EMPTY;
+            }
+
+            return new SeekingTermSetTermsEnum(terms.Iterator(null), _terms, _ords);
+
+        }
+
+        public override string ToString(string field)
+        {
+            return string.Format("TermsQuery{{field={0}}}", field);
+        }
+
+        private class SeekingTermSetTermsEnum : FilteredTermsEnum
+        {
+            private readonly BytesRefHash Terms;
+            private readonly int[] Ords;
+            private readonly int _lastElement;
+
+            private readonly BytesRef _lastTerm;
+            private readonly BytesRef _spare = new BytesRef();
+            private readonly IComparer<BytesRef> _comparator;
+
+            private BytesRef _seekTerm;
+            private int _upto;
+
+            internal SeekingTermSetTermsEnum(TermsEnum tenum, BytesRefHash terms, int[] ords) : base(tenum)
+            {
+                Terms = terms;
+                Ords = ords;
+                _comparator = BytesRef.UTF8SortedAsUnicodeComparer;
+                _lastElement = terms.Size() - 1;
+                _lastTerm = terms.Get(ords[_lastElement], new BytesRef());
+                _seekTerm = terms.Get(ords[_upto], _spare);
+            }
+
+
+            
+            protected override BytesRef NextSeekTerm(BytesRef currentTerm)
+            {
+                BytesRef temp = _seekTerm;
+                _seekTerm = null;
+                return temp;
+            }
+            
+            protected override AcceptStatus Accept(BytesRef term)
+            {
+                if (_comparator.Compare(term, _lastTerm) > 0)
+                {
+                    return AcceptStatus.END;
+                }
+
+                BytesRef currentTerm = Terms.Get(Ords[_upto], _spare);
+                if (_comparator.Compare(term, currentTerm) == 0)
+                {
+                    if (_upto == _lastElement)
+                    {
+                        return AcceptStatus.YES;
+                    }
+
+                    _seekTerm = Terms.Get(Ords[++_upto], _spare);
+                    return AcceptStatus.YES_AND_SEEK;
+                }
+
+                if (_upto == _lastElement)
+                {
+                    return AcceptStatus.NO;
+                } // Our current term doesn't match the the given term.
+
+                int cmp;
+                do // We maybe are behind the given term by more than one step. Keep incrementing till we're the same or higher.
+                {
+                    if (_upto == _lastElement)
+                    {
+                        return AcceptStatus.NO;
+                    }
+                    // typically the terms dict is a superset of query's terms so it's unusual that we have to skip many of
+                    // our terms so we don't do a binary search here
+                    _seekTerm = Terms.Get(Ords[++_upto], _spare);
+                } while ((cmp = _comparator.Compare(_seekTerm, term)) < 0);
+                if (cmp == 0)
+                {
+                    if (_upto == _lastElement)
+                    {
+                        return AcceptStatus.YES;
+                    }
+                    _seekTerm = Terms.Get(Ords[++_upto], _spare);
+                    return AcceptStatus.YES_AND_SEEK;
+                }
+
+                return AcceptStatus.NO_AND_SEEK;
+            }
+        }
+    }
+}
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/lucenenet/blob/4820f236/src/Lucene.Net.Join/TermsWithScoreCollector.cs
----------------------------------------------------------------------
diff --git a/src/Lucene.Net.Join/TermsWithScoreCollector.cs b/src/Lucene.Net.Join/TermsWithScoreCollector.cs
new file mode 100644
index 0000000..e823293
--- /dev/null
+++ b/src/Lucene.Net.Join/TermsWithScoreCollector.cs
@@ -0,0 +1,333 @@
+using System;
+using Lucene.Net.Index;
+using Lucene.Net.Search;
+using Lucene.Net.Util;
+
+namespace Lucene.Net.Join
+{
+    /*
+	 * 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.
+	 */
+
+
+    internal abstract class TermsWithScoreCollector : Collector
+    {
+        private const int InitialArraySize = 256;
+
+        private readonly string _field;
+        private readonly BytesRefHash _collectedTerms = new BytesRefHash();
+        private readonly ScoreMode _scoreMode;
+
+        private Scorer _scorer;
+        private float[] _scoreSums = new float[InitialArraySize];
+
+        internal TermsWithScoreCollector(string field, ScoreMode scoreMode)
+        {
+            this._field = field;
+            this._scoreMode = scoreMode;
+        }
+
+        public BytesRefHash CollectedTerms
+        {
+            get
+            {
+                return _collectedTerms;
+            }
+        }
+
+        public virtual float[] ScoresPerTerm
+        {
+            get
+            {
+                return _scoreSums;
+            }
+        }
+
+        //JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
+        //ORIGINAL LINE: @Override public void setScorer(org.apache.lucene.search.Scorer scorer) throws java.io.IOException
+        public override Scorer Scorer
+        {
+            set
+            {
+                _scorer = value;
+            }
+        }
+
+        public override bool AcceptsDocsOutOfOrder()
+        {
+            return true;
+        }
+
+        /// <summary>
+        /// Chooses the right <seealso cref="TermsWithScoreCollector"/> implementation.
+        /// </summary>
+        /// <param name="field">The field to collect terms for.</param>
+        /// <param name="multipleValuesPerDocument">Whether the field to collect terms for has multiple values per document.</param>
+        /// <returns>A <see cref="TermsWithScoreCollector"/> instance</returns>
+        internal static TermsWithScoreCollector Create(string field, bool multipleValuesPerDocument, ScoreMode scoreMode)
+        {
+            if (multipleValuesPerDocument)
+            {
+                switch (scoreMode)
+                {
+                    case ScoreMode.Avg:
+                        return new Mv.Avg(field);
+                    default:
+                        return new Mv(field, scoreMode);
+                }
+            }
+
+            switch (scoreMode)
+            {
+                case ScoreMode.Avg:
+                    return new Sv.Avg(field);
+                default:
+                    return new Sv(field, scoreMode);
+            }
+        }
+
+        // impl that works with single value per document
+        internal class Sv : TermsWithScoreCollector
+        {
+            private readonly BytesRef _spare = new BytesRef();
+            private BinaryDocValues _fromDocTerms;
+
+            internal Sv(string field, ScoreMode scoreMode) : base(field, scoreMode)
+            {
+            }
+            
+            public override void Collect(int doc)
+            {
+                _fromDocTerms.Get(doc, _spare);
+                int ord = _collectedTerms.Add(_spare);
+                if (ord < 0)
+                {
+                    ord = -ord - 1;
+                }
+                else
+                {
+                    if (ord >= _scoreSums.Length)
+                    {
+                        _scoreSums = ArrayUtil.Grow(_scoreSums);
+                    }
+                }
+
+                float current = _scorer.Score();
+                float existing = _scoreSums[ord];
+                if (existing.CompareTo(0.0f) == 0)
+                {
+                    _scoreSums[ord] = current;
+                }
+                else
+                {
+                    switch (_scoreMode)
+                    {
+                        case ScoreMode.Total:
+                            _scoreSums[ord] = _scoreSums[ord] + current;
+                            break;
+                        case ScoreMode.Max:
+                            if (current > existing)
+                            {
+                                _scoreSums[ord] = current;
+                            }
+                            break;
+                    }
+                }
+            }
+            
+            public override AtomicReaderContext NextReader
+            {
+                set
+                {
+                    _fromDocTerms = FieldCache.DEFAULT.GetTerms(value.AtomicReader, _field, false);
+                }
+            }
+
+            public override bool AcceptsDocsOutOfOrder()
+            {
+                return base.AcceptsDocsOutOfOrder();
+            }
+
+            internal class Avg : Sv
+            {
+                private int[] _scoreCounts = new int[InitialArraySize];
+
+                internal Avg(string field) : base(field, ScoreMode.Avg)
+                {
+                }
+                
+                public override void Collect(int doc)
+                {
+                    _fromDocTerms.Get(doc, _spare);
+                    int ord = _collectedTerms.Add(_spare);
+                    if (ord < 0)
+                    {
+                        ord = -ord - 1;
+                    }
+                    else
+                    {
+                        if (ord >= _scoreSums.Length)
+                        {
+                            _scoreSums = ArrayUtil.Grow(_scoreSums);
+                            _scoreCounts = ArrayUtil.Grow(_scoreCounts);
+                        }
+                    }
+
+                    float current = _scorer.Score();
+                    float existing = _scoreSums[ord];
+                    if (existing.CompareTo(0.0f) == 0)
+                    {
+                        _scoreSums[ord] = current;
+                        _scoreCounts[ord] = 1;
+                    }
+                    else
+                    {
+                        _scoreSums[ord] = _scoreSums[ord] + current;
+                        _scoreCounts[ord]++;
+                    }
+                }
+
+                public override float[] ScoresPerTerm
+                {
+                    get
+                    {
+                        if (_scoreCounts != null)
+                        {
+                            for (int i = 0; i < _scoreCounts.Length; i++)
+                            {
+                                _scoreSums[i] = _scoreSums[i] / _scoreCounts[i];
+                            }
+                            _scoreCounts = null;
+                        }
+                        return _scoreSums;
+                    }
+                }
+            }
+        }
+
+        // impl that works with multiple values per document
+        internal class Mv : TermsWithScoreCollector
+        {
+            private SortedSetDocValues _fromDocTermOrds;
+            private readonly BytesRef _scratch = new BytesRef();
+
+            internal Mv(string field, ScoreMode scoreMode) : base(field, scoreMode)
+            {
+            }
+            
+            public override void Collect(int doc)
+            {
+                _fromDocTermOrds.Document = doc;
+                long ord;
+                while ((ord = _fromDocTermOrds.NextOrd()) != SortedSetDocValues.NO_MORE_ORDS)
+                {
+                    _fromDocTermOrds.LookupOrd(ord, _scratch);
+
+                    int termId = _collectedTerms.Add(_scratch);
+                    if (termId < 0)
+                    {
+                        termId = -termId - 1;
+                    }
+                    else
+                    {
+                        if (termId >= _scoreSums.Length)
+                        {
+                            _scoreSums = ArrayUtil.Grow(_scoreSums);
+                        }
+                    }
+
+                    switch (_scoreMode)
+                    {
+                        case ScoreMode.Total:
+                            _scoreSums[termId] += _scorer.Score();
+                            break;
+                        case ScoreMode.Max:
+                            _scoreSums[termId] = Math.Max(_scoreSums[termId], _scorer.Score());
+                            break;
+                    }
+                }
+            }
+
+            //JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
+            //ORIGINAL LINE: @Override public void setNextReader(org.apache.lucene.index.AtomicReaderContext context) throws java.io.IOException
+            public override AtomicReaderContext NextReader
+            {
+                set
+                {
+                    _fromDocTermOrds = FieldCache.DEFAULT.GetDocTermOrds(value.AtomicReader, _field);
+                }
+            }
+
+            public override bool AcceptsDocsOutOfOrder()
+            {
+                throw new NotImplementedException();
+            }
+
+            internal class Avg : Mv
+            {
+                private int[] _scoreCounts = new int[InitialArraySize];
+
+                internal Avg(string field) : base(field, ScoreMode.Avg)
+                {
+                }
+                
+                public override void Collect(int doc)
+                {
+                    _fromDocTermOrds.Document = doc;
+                    long ord;
+                    while ((ord = _fromDocTermOrds.NextOrd()) != SortedSetDocValues.NO_MORE_ORDS)
+                    {
+                        _fromDocTermOrds.LookupOrd(ord, _scratch);
+
+                        int termId = _collectedTerms.Add(_scratch);
+                        if (termId < 0)
+                        {
+                            termId = -termId - 1;
+                        }
+                        else
+                        {
+                            if (termId >= _scoreSums.Length)
+                            {
+                                _scoreSums = ArrayUtil.Grow(_scoreSums);
+                                _scoreCounts = ArrayUtil.Grow(_scoreCounts);
+                            }
+                        }
+
+                        _scoreSums[termId] += _scorer.Score();
+                        _scoreCounts[termId]++;
+                    }
+                }
+
+                public override float[] ScoresPerTerm
+                {
+                    get
+                    {
+                        if (_scoreCounts != null)
+                        {
+                            for (int i = 0; i < _scoreCounts.Length; i++)
+                            {
+                                _scoreSums[i] = _scoreSums[i] / _scoreCounts[i];
+                            }
+                            _scoreCounts = null;
+                        }
+                        return _scoreSums;
+                    }
+                }
+            }
+        }
+
+    }
+}
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/lucenenet/blob/4820f236/src/Lucene.Net.Join/ToChildBlockJoinQuery.cs
----------------------------------------------------------------------
diff --git a/src/Lucene.Net.Join/ToChildBlockJoinQuery.cs b/src/Lucene.Net.Join/ToChildBlockJoinQuery.cs
new file mode 100644
index 0000000..3d4f2d5
--- /dev/null
+++ b/src/Lucene.Net.Join/ToChildBlockJoinQuery.cs
@@ -0,0 +1,396 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using Lucene.Net.Index;
+using Lucene.Net.Search;
+using Lucene.Net.Util;
+
+namespace Lucene.Net.Join
+{
+    /*
+	 * 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.
+	 */
+
+    /// <summary>
+    /// Just like <see cref="ToParentBlockJoinQuery"/>, except this
+    /// query joins in reverse: you provide a Query matching
+    /// parent documents and it joins down to child
+    /// documents.
+    /// 
+    /// @lucene.experimental
+    /// </summary>
+    public class ToChildBlockJoinQuery : Query
+    {
+        /// <summary>
+        /// Message thrown from <see cref="ToChildBlockJoinScorer.ValidateParentDoc"/>
+        /// on mis-use, when the parent query incorrectly returns child docs. 
+        /// </summary>
+        public const string InvalidQueryMessage = "Parent query yields document which is not matched by parents filter, docID=";
+
+        private readonly Filter _parentsFilter;
+        private readonly Query _parentQuery;
+
+        // If we are rewritten, this is the original parentQuery we
+        // were passed; we use this for .equals() and
+        // .hashCode().  This makes rewritten query equal the
+        // original, so that user does not have to .rewrite() their
+        // query before searching:
+        private readonly Query _origParentQuery;
+        private readonly bool _doScores;
+
+        /// <summary>
+        /// Create a ToChildBlockJoinQuery.
+        /// </summary>
+        /// <param name="parentQuery">Query that matches parent documents</param>
+        /// <param name="parentsFilter">Filter (must produce FixedBitSet per-segment, like <see cref="FixedBitSetCachingWrapperFilter"/>) 
+        /// identifying the parent documents.</param>
+        /// <param name="doScores">True if parent scores should be calculated.</param>
+        public ToChildBlockJoinQuery(Query parentQuery, Filter parentsFilter, bool doScores)
+        {
+            _origParentQuery = parentQuery;
+            _parentQuery = parentQuery;
+            _parentsFilter = parentsFilter;
+            _doScores = doScores;
+        }
+
+        private ToChildBlockJoinQuery(Query origParentQuery, Query parentQuery, Filter parentsFilter, bool doScores) : base()
+        {
+            _origParentQuery = origParentQuery;
+            _parentQuery = parentQuery;
+            _parentsFilter = parentsFilter;
+            _doScores = doScores;
+        }
+        
+        public override Weight CreateWeight(IndexSearcher searcher)
+        {
+            return new ToChildBlockJoinWeight(this, _parentQuery.CreateWeight(searcher), _parentsFilter, _doScores);
+        }
+
+        private class ToChildBlockJoinWeight : Weight
+        {
+            private readonly Query _joinQuery;
+            private readonly Weight _parentWeight;
+            private readonly Filter _parentsFilter;
+            private readonly bool _doScores;
+
+            public ToChildBlockJoinWeight(Query joinQuery, Weight parentWeight, Filter parentsFilter, bool doScores) : base()
+            {
+                _joinQuery = joinQuery;
+                _parentWeight = parentWeight;
+                _parentsFilter = parentsFilter;
+                _doScores = doScores;
+            }
+
+            public override Query Query
+            {
+                get { return _joinQuery; }
+            }
+            
+            public override float ValueForNormalization
+            {
+                get { return _parentWeight.ValueForNormalization*_joinQuery.Boost*_joinQuery.Boost; }
+            }
+
+            public override void Normalize(float norm, float topLevelBoost)
+            {
+                _parentWeight.Normalize(norm, topLevelBoost * _joinQuery.Boost);
+            }
+
+            // NOTE: acceptDocs applies (and is checked) only in the child document space
+            public override Scorer Scorer(AtomicReaderContext readerContext, Bits acceptDocs)
+            {
+                Scorer parentScorer = _parentWeight.Scorer(readerContext, null);
+
+                if (parentScorer == null)
+                {
+                    // No matches
+                    return null;
+                }
+
+                // NOTE: we cannot pass acceptDocs here because this
+                // will (most likely, justifiably) cause the filter to
+                // not return a FixedBitSet but rather a
+                // BitsFilteredDocIdSet.  Instead, we filter by
+                // acceptDocs when we score:
+                DocIdSet parents = _parentsFilter.GetDocIdSet(readerContext, null);
+
+                if (parents == null)
+                {
+                    // No matches
+                    return null;
+                }
+                if (!(parents is FixedBitSet))
+                {
+                    throw new InvalidOperationException("parentFilter must return FixedBitSet; got " + parents);
+                }
+
+                return new ToChildBlockJoinScorer(this, parentScorer, (FixedBitSet)parents, _doScores, acceptDocs);
+            }
+            
+            public override Explanation Explain(AtomicReaderContext reader, int doc)
+            {
+                // TODO
+                throw new NotSupportedException(GetType().Name + " cannot explain match on parent document");
+            }
+
+            public override bool ScoresDocsOutOfOrder()
+            {
+                return false;
+            }
+        }
+
+        private sealed class ToChildBlockJoinScorer : Scorer
+        {
+            private readonly Scorer _parentScorer;
+            private readonly FixedBitSet _parentBits;
+            private readonly bool _doScores;
+            private readonly Bits _acceptDocs;
+
+            private float _parentScore;
+            private int _parentFreq = 1;
+
+            private int _childDoc = -1;
+            private int _parentDoc;
+
+            public ToChildBlockJoinScorer(Weight weight, Scorer parentScorer, FixedBitSet parentBits, bool doScores, Bits acceptDocs) : base(weight)
+            {
+                _doScores = doScores;
+                _parentBits = parentBits;
+                _parentScorer = parentScorer;
+                _acceptDocs = acceptDocs;
+            }
+
+            public override ICollection<ChildScorer> Children
+            {
+                get { return Collections.Singleton(new ChildScorer(_parentScorer, "BLOCK_JOIN")); }
+            }
+            
+            public override int NextDoc()
+            {
+                //System.out.println("Q.nextDoc() parentDoc=" + parentDoc + " childDoc=" + childDoc);
+
+                // Loop until we hit a childDoc that's accepted
+                while (true)
+                {
+                    if (_childDoc + 1 == _parentDoc)
+                    {
+                        // OK, we are done iterating through all children
+                        // matching this one parent doc, so we now nextDoc()
+                        // the parent.  Use a while loop because we may have
+                        // to skip over some number of parents w/ no
+                        // children:
+                        while (true)
+                        {
+                            _parentDoc = _parentScorer.NextDoc();
+                            ValidateParentDoc();
+
+                            if (_parentDoc == 0)
+                            {
+                                // Degenerate but allowed: first parent doc has no children
+                                // TODO: would be nice to pull initial parent
+                                // into ctor so we can skip this if... but it's
+                                // tricky because scorer must return -1 for
+                                // .doc() on init...
+                                _parentDoc = _parentScorer.NextDoc();
+                                ValidateParentDoc();
+                            }
+
+                            if (_parentDoc == NO_MORE_DOCS)
+                            {
+                                _childDoc = NO_MORE_DOCS;
+                                //System.out.println("  END");
+                                return _childDoc;
+                            }
+
+                            // Go to first child for this next parentDoc:
+                            _childDoc = 1 + _parentBits.PrevSetBit(_parentDoc - 1);
+
+                            if (_childDoc == _parentDoc)
+                            {
+                                // This parent has no children; continue
+                                // parent loop so we move to next parent
+                                continue;
+                            }
+
+                            if (_acceptDocs != null && !_acceptDocs.Get(_childDoc))
+                            {
+                                goto nextChildDocContinue;
+                            }
+
+                            if (_childDoc < _parentDoc)
+                            {
+                                if (_doScores)
+                                {
+                                    _parentScore = _parentScorer.Score();
+                                    _parentFreq = _parentScorer.Freq();
+                                }
+                                //System.out.println("  " + childDoc);
+                                return _childDoc;
+                            }
+                            else
+                            {
+                                // Degenerate but allowed: parent has no children
+                            }
+                        }
+                    }
+
+                    Debug.Assert(_childDoc < _parentDoc, "childDoc=" + _childDoc + " parentDoc=" + _parentDoc);
+                    _childDoc++;
+                    if (_acceptDocs != null && !_acceptDocs.Get(_childDoc))
+                    {
+                        continue;
+                    }
+                    //System.out.println("  " + childDoc);
+                    return _childDoc;
+                    nextChildDocContinue:;
+                }
+            }
+
+            /// <summary>
+            /// Detect mis-use, where provided parent query in fact sometimes returns child documents.  
+            /// </summary>
+            private void ValidateParentDoc()
+            {
+                if (_parentDoc != NO_MORE_DOCS && !_parentBits.Get(_parentDoc))
+                {
+                    throw new InvalidOperationException(InvalidQueryMessage + _parentDoc);
+                }
+            }
+
+            public override int DocID()
+            {
+                return _childDoc;
+            }
+            
+            public override float Score()
+            {
+                return _parentScore;
+            }
+            
+            public override int Freq()
+            {
+                return _parentFreq;
+            }
+            
+            public override int Advance(int childTarget)
+            {
+                Debug.Assert(childTarget >= _parentBits.Length() || !_parentBits.Get(childTarget));
+
+                //System.out.println("Q.advance childTarget=" + childTarget);
+                if (childTarget == NO_MORE_DOCS)
+                {
+                    //System.out.println("  END");
+                    return _childDoc = _parentDoc = NO_MORE_DOCS;
+                }
+
+                Debug.Assert(_childDoc == -1 || childTarget != _parentDoc, "childTarget=" + childTarget);
+                if (_childDoc == -1 || childTarget > _parentDoc)
+                {
+                    // Advance to new parent:
+                    _parentDoc = _parentScorer.Advance(childTarget);
+                    ValidateParentDoc();
+                    //System.out.println("  advance to parentDoc=" + parentDoc);
+                    Debug.Assert(_parentDoc > childTarget);
+                    if (_parentDoc == NO_MORE_DOCS)
+                    {
+                        //System.out.println("  END");
+                        return _childDoc = NO_MORE_DOCS;
+                    }
+                    if (_doScores)
+                    {
+                        _parentScore = _parentScorer.Score();
+                        _parentFreq = _parentScorer.Freq();
+                    }
+                    int firstChild = _parentBits.PrevSetBit(_parentDoc - 1);
+                    //System.out.println("  firstChild=" + firstChild);
+                    childTarget = Math.Max(childTarget, firstChild);
+                }
+
+                Debug.Assert(childTarget < _parentDoc);
+
+                // Advance within children of current parent:
+                _childDoc = childTarget;
+                //System.out.println("  " + childDoc);
+                if (_acceptDocs != null && !_acceptDocs.Get(_childDoc))
+                {
+                    NextDoc();
+                }
+                return _childDoc;
+            }
+
+            public override long Cost()
+            {
+                return _parentScorer.Cost();
+            }
+        }
+
+        public override void ExtractTerms(ISet<Term> terms)
+        {
+            _parentQuery.ExtractTerms(terms);
+        }
+        
+        public override Query Rewrite(IndexReader reader)
+        {
+            Query parentRewrite = _parentQuery.Rewrite(reader);
+            if (parentRewrite != _parentQuery)
+            {
+                Query rewritten = new ToChildBlockJoinQuery(_parentQuery, parentRewrite, _parentsFilter, _doScores);
+                rewritten.Boost = Boost;
+                return rewritten;
+            }
+
+            return this;
+        }
+
+        public override string ToString(string field)
+        {
+            return "ToChildBlockJoinQuery (" + _parentQuery + ")";
+        }
+
+        protected bool Equals(ToChildBlockJoinQuery other)
+        {
+            return base.Equals(other) && 
+                Equals(_origParentQuery, other._origParentQuery) && 
+                _doScores == other._doScores &&
+                Equals(_parentsFilter, other._parentsFilter);
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (ReferenceEquals(null, obj)) return false;
+            if (ReferenceEquals(this, obj)) return true;
+            if (obj.GetType() != GetType()) return false;
+            return Equals((ToChildBlockJoinQuery) obj);
+        }
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                int hashCode = base.GetHashCode();
+                hashCode = (hashCode*397) ^ (_origParentQuery != null ? _origParentQuery.GetHashCode() : 0);
+                hashCode = (hashCode*397) ^ _doScores.GetHashCode();
+                hashCode = (hashCode*397) ^ (_parentsFilter != null ? _parentsFilter.GetHashCode() : 0);
+                return hashCode;
+            }
+        }
+
+        public override object Clone()
+        {
+            return new ToChildBlockJoinQuery((Query) _origParentQuery.Clone(), _parentsFilter, _doScores);
+        }
+    }
+}
\ No newline at end of file