CSHARP-4768: Introduce $vectorSearch aggregation stage (#1187)

src/MongoDB.Driver.Core/Core/Misc/Ensure.cs

@@ -267,6 +267,34 @@ public static string IsNotNullOrEmpty(string value, string paramName)
             return value;
         }
 
+        /// <summary>
+        /// Ensures that the value of a parameter is not null or empty.
+        /// </summary>
+        /// <param name="value">The value of the parameter.</param>
+        /// <param name="paramName">The name of the parameter.</param>
+        /// <returns>The value of the parameter.</returns>
+        public static IEnumerable<T> IsNotNullOrEmpty<T>(IEnumerable<T> value, string paramName)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(paramName);
+            }
+
+            if (value is ICollection<T> collection)
+            {
+                if (collection.Count == 0)
+                {
+                    throw new ArgumentException("Value cannot be empty.", paramName);
+                }
+            }
+            else if (!value.Any())
+            {
+                throw new ArgumentException("Value cannot be empty.", paramName);
+            }
+
+            return value;
+        }
+
         /// <summary>
         /// Ensures that the value of a parameter is null.
         /// </summary>

src/MongoDB.Driver/AggregateFluent.cs

@@ -346,6 +346,15 @@ public override IAggregateFluent<TNewResult> Unwind<TNewResult>(FieldDefinition<
             return WithPipeline(_pipeline.Unwind(field, options));
         }
 
+        public override IAggregateFluent<TResult> VectorSearch(
+            FieldDefinition<TResult> field,
+            QueryVector queryVector,
+            int limit,
+            VectorSearchOptions<TResult> options = null)
+        {
+            return WithPipeline(_pipeline.VectorSearch(field, queryVector, limit, options));
+        }
+
         public override string ToString()
         {
             var linqProvider = Database.Client.Settings.LinqProvider;

src/MongoDB.Driver/AggregateFluentBase.cs

@@ -307,6 +307,16 @@ public virtual IAggregateFluent<TNewResult> Unwind<TNewResult>(FieldDefinition<T
             throw new NotImplementedException();
         }
 
+        /// <inheritdoc />
+        public virtual IAggregateFluent<TResult> VectorSearch(
+            FieldDefinition<TResult> field,
+            QueryVector queryVector,
+            int limit,
+            VectorSearchOptions<TResult> options = null)
+        {
+            throw new NotImplementedException();
+        }
+
         /// <inheritdoc />
         public virtual void ToCollection(CancellationToken cancellationToken)
         {

src/MongoDB.Driver/IAggregateFluent.cs

@@ -501,6 +501,20 @@ IAggregateFluent<TResult> UnionWith<TWith>(
         /// <param name="options">The options.</param>
         /// <returns>The fluent aggregate interface.</returns>
         IAggregateFluent<TNewResult> Unwind<TNewResult>(FieldDefinition<TResult> field, AggregateUnwindOptions<TNewResult> options = null);
+
+        /// <summary>
+        /// Appends a vector search stage.
+        /// </summary>
+        /// <param name="field">The field.</param>
+        /// <param name="queryVector">The query vector.</param>
+        /// <param name="limit">The limit.</param>
+        /// <param name="options">The vector search options.</param>
+        /// <returns>The fluent aggregate interface.</returns>
+        IAggregateFluent<TResult> VectorSearch(
+            FieldDefinition<TResult> field,
+            QueryVector queryVector,
+            int limit,
+            VectorSearchOptions<TResult> options = null);
     }
 
     /// <summary>

src/MongoDB.Driver/IAggregateFluentExtensions.cs

@@ -967,5 +967,27 @@ public static IAggregateFluent<TNewResult> Unwind<TResult, TNewResult>(this IAgg
 
             return IAsyncCursorSourceExtensions.SingleOrDefaultAsync(aggregate.Limit(2), cancellationToken);
         }
+
+        /// <summary>
+        /// Appends a $vectorSearch stage.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result.</typeparam>
+        /// <param name="aggregate">The aggregate.</param>
+        /// <param name="field">The field.</param>
+        /// <param name="queryVector">The query vector.</param>
+        /// <param name="limit">The limit.</param>
+        /// <param name="options">The vector search options.</param>
+        /// <returns>The fluent aggregate interface.</returns>
+        public static IAggregateFluent<TResult> VectorSearch<TResult>(
+            this IAggregateFluent<TResult> aggregate,
+            Expression<Func<TResult, object>> field,
+            QueryVector queryVector,
+            int limit,
+            VectorSearchOptions<TResult> options = null)
+        {
+            Ensure.IsNotNull(aggregate, nameof(aggregate));
+
+            return aggregate.VectorSearch(new ExpressionFieldDefinition<TResult>(field), queryVector, limit, options);
+        }
     }
 }

src/MongoDB.Driver/Linq/MongoQueryable.cs

@@ -3484,6 +3484,56 @@ public static IOrderedMongoQueryable<TSource> ThenByDescending<TSource, TKey>(th
             return (IOrderedMongoQueryable<TSource>)Queryable.ThenByDescending(source, keySelector);
         }
 
+        /// <summary>
+        /// Appends a $vectorSearch stage to the LINQ pipeline.
+        /// </summary>
+        /// <typeparam name="TSource">The type of the elements of <paramref name="source" />.</typeparam>
+        /// <typeparam name="TField">The type of the field.</typeparam>
+        /// <param name="source">A sequence of values.</param>
+        /// <param name="field">The field.</param>
+        /// <param name="queryVector">The query vector.</param>
+        /// <param name="limit">The limit.</param>
+        /// <param name="options">The options.</param>
+        /// <returns>
+        /// The queryable with a new stage appended.
+        /// </returns>
+        public static IMongoQueryable<TSource> VectorSearch<TSource, TField>(
+            this IMongoQueryable<TSource> source,
+            FieldDefinition<TSource> field,
+            QueryVector queryVector,
+            int limit,
+            VectorSearchOptions<TSource> options = null)
+        {
+            return AppendStage(
+                source,
+                PipelineStageDefinitionBuilder.VectorSearch(field, queryVector, limit, options));
+        }
+
+        /// <summary>
+        /// Appends a $vectorSearch stage to the LINQ pipeline.
+        /// </summary>
+        /// <typeparam name="TSource">The type of the elements of <paramref name="source" />.</typeparam>
+        /// <typeparam name="TField">The type of the field.</typeparam>
+        /// <param name="source">A sequence of values.</param>
+        /// <param name="field">The field.</param>
+        /// <param name="queryVector">The query vector.</param>
+        /// <param name="limit">The limit.</param>
+        /// <param name="options">The options.</param>
+        /// <returns>
+        /// The queryable with a new stage appended.
+        /// </returns>
+        public static IMongoQueryable<TSource> VectorSearch<TSource, TField>(
+            this IMongoQueryable<TSource> source,
+            Expression<Func<TSource, TField>> field,
+            QueryVector queryVector,
+            int limit,
+            VectorSearchOptions<TSource> options = null)
+        {
+            return AppendStage(
+                source,
+                PipelineStageDefinitionBuilder.VectorSearch(field, queryVector, limit, options));
+        }
+
         /// <summary>
         /// Filters a sequence of values based on a predicate.
         /// </summary>