has_parent filter was added in 0.19.10

src/Nest.Tests.Unit/Nest.Tests.Unit.csproj

@@ -107,6 +107,7 @@
     <Compile Include="Internals\Inferno\HostNameWithPathTests.cs" />
     <Compile Include="Internals\Inferno\MapTypeNamesTests.cs" />
     <Compile Include="Internals\Serialize\OptOutTests.cs" />
+    <Compile Include="Search\Filter\Singles\HasParentFilterJson.cs" />
     <Compile Include="Search\Rescore\RescoreTests.cs" />
     <Compile Include="Search\Facets\DateHistogramFacetJson.cs" />
     <Compile Include="Search\Facets\FacetJson.cs" />

src/Nest.Tests.Unit/Search/Filter/Singles/HasChildFilterJson.cs

@@ -33,7 +33,7 @@ public void HasChildFilter()
 					}
 				}
 			}";
-			Assert.True(json.JsonEquals(expected), json);		
+			Assert.True(json.JsonEquals(expected), json);
 		}
 	}
 }

src/Nest.Tests.Unit/Search/Filter/Singles/HasParentFilterJson.cs

@@ -0,0 +1,39 @@
+using NUnit.Framework;
+using Nest.Tests.MockData.Domain;
+
+namespace Nest.Tests.Unit.Search.Filter.Singles
+{
+	[TestFixture]
+	public class HasParentFilterJson
+	{
+		[Test]
+		public void HasParentFilter()
+		{
+			var s = new SearchDescriptor<Person>().From(0).Size(10)
+				.Filter(ff=>ff
+					.HasParent<ElasticSearchProject>(d=>d
+						.Scope("my_scope")
+						.Query(q=>q.Term(p=>p.Country, "value"))
+					)
+				);
+
+			var json = TestElasticClient.Serialize(s);
+			var expected = @"{ from: 0, size: 10, 
+				filter : {
+					""has_parent"": {
+					  ""type"": ""elasticsearchprojects"",
+					  ""_scope"": ""my_scope"",
+					  ""query"": {
+						""term"": {
+						  ""country"": {
+							""value"": ""value""
+						  }
+						}
+					  }
+					}
+				}
+			}";
+			Assert.True(json.JsonEquals(expected), json);		
+		}
+	}
+}

src/Nest/DSL/Filter/HasParentFilterDescriptor.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using Newtonsoft.Json;
+using System.Linq.Expressions;
+using Nest.Resolvers;
+
+namespace Nest
+{
+	[JsonObject(MemberSerialization=MemberSerialization.OptIn)]
+	public class HasParentFilterDescriptor<T> : FilterBase where T : class
+	{
+		public HasParentFilterDescriptor()
+		{
+			this._Type = new TypeNameResolver().GetTypeNameFor<T>();
+		}
+		internal override bool IsConditionless
+		{
+			get
+			{
+				return this._QueryDescriptor == null || this._QueryDescriptor.IsConditionless || this._Type.IsNullOrEmpty();
+			}
+		}
+
+		[JsonProperty("type")]
+		internal TypeNameMarker _Type { get; set; }
+
+		[JsonProperty("_scope")]
+		internal string _Scope { get; set;}
+
+		[JsonProperty("query")]
+		internal BaseQuery _QueryDescriptor { get; set; }
+
+		public HasParentFilterDescriptor<T> Query(Func<QueryDescriptor<T>, BaseQuery> querySelector)
+		{
+			var q = new QueryDescriptor<T>();
+			this._QueryDescriptor = querySelector(q);
+			return this;
+		}
+
+		public HasParentFilterDescriptor<T> Scope(string scope)
+		{
+			this._Scope = scope;
+			return this;
+		}
+		public HasParentFilterDescriptor<T> Type(string type)
+		{
+			this._Type = type;
+			return this;
+		}
+	}
+}

src/Nest/DSL/FilterDescriptor.cs

@@ -75,6 +75,9 @@ public FilterDescriptor<T> Cache(bool cache)
 		[JsonProperty(PropertyName = "has_child")]
 		internal object HasChildFilter { get; set; }
 
+		[JsonProperty(PropertyName = "has_parent")]
+		internal object HasParentFilter { get; set; }
+
 		[JsonProperty(PropertyName = "numeric_range")]
 		internal Dictionary<string, object> NumericRangeFilter { get; set; }
 
@@ -150,6 +153,7 @@ internal FilterDescriptor<T> Clone()
 				TypeFilter = TypeFilter,
 				MatchAllFilter = MatchAllFilter,
 				HasChildFilter = HasChildFilter,
+				HasParentFilter = HasParentFilter,
 				NumericRangeFilter = NumericRangeFilter,
 				RangeFilter = RangeFilter,
 				PrefixFilter = PrefixFilter,
@@ -498,6 +502,26 @@ public BaseFilter HasChild<K>(Action<HasChildFilterDescriptor<K>> filterSelector
 
 			return new FilterDescriptor<T>() { HasChildFilter = filter };
 		}
+
+		/// <summary>
+		/// The has_child filter accepts a query and the child type to run against, 
+		/// and results in parent documents that have child docs matching the query.
+		/// </summary>
+		/// <typeparam name="K">Type of the child</typeparam>
+		public BaseFilter HasParent<K>(Action<HasParentFilterDescriptor<K>> filterSelector) where K : class
+		{
+			var filter = new HasParentFilterDescriptor<K>();
+			if (filterSelector == null)
+				return CreateConditionlessFilterDescriptor("has_parent", filter);
+
+			filterSelector(filter);
+
+			if (filter.IsConditionless)
+				return CreateConditionlessFilterDescriptor("has_parent", filter);
+
+			return new FilterDescriptor<T>() { HasParentFilter = filter };
+		}
+
 		/// <summary>
 		/// A limit filter limits the number of documents (per shard) to execute on.
 		/// </summary>

src/Nest/DSL/IFilterDescriptor.cs

@@ -23,6 +23,7 @@ interface IFilterDescriptor<T>
 		BaseFilter GeoPolygon(string field, IEnumerable<Tuple<double, double>> points);
 		BaseFilter GeoPolygon(string fieldName, params string[] points);
 		BaseFilter HasChild<K>(Action<HasChildFilterDescriptor<K>> querySelector) where K : class;
+		BaseFilter HasParent<K>(Action<HasParentFilterDescriptor<K>> querySelector) where K : class;
 		BaseFilter Ids(IEnumerable<string> types, IEnumerable<string> values);
 		BaseFilter Ids(IEnumerable<string> values);
 		BaseFilter Ids(string type, IEnumerable<string> values);

src/Nest/Nest.csproj

@@ -70,6 +70,7 @@
     <Compile Include="Domain\Connection\ConnectionStatusTracer.cs" />
     <Compile Include="Domain\PathAndData.cs" />
     <Compile Include="DSL\BulkUpdateDescriptor.cs" />
+    <Compile Include="DSL\Filter\HasParentFilterDescriptor.cs" />
     <Compile Include="DSL\PercolatorDescriptor.cs" />
     <Compile Include="DSL\PercolateDescriptor.cs" />
     <Compile Include="Extensions\NameValueCollectionExtensions.cs" />