Map List<T> operations to PostgreSQL arrays

src/EFCore.PG/Query/ExpressionTranslators/Internal/NpgsqlArrayFragmentTranslator.cs

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+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq.Expressions;
+using System.Reflection;
+using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Query.ExpressionTranslators;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Query.Expressions.Internal;
+using Remotion.Linq;
+using Remotion.Linq.Clauses;
+using Remotion.Linq.Clauses.Expressions;
+using Remotion.Linq.Clauses.ResultOperators;
+
+namespace Npgsql.EntityFrameworkCore.PostgreSQL.Query.ExpressionTranslators.Internal
+{
+    /// <summary>
+    /// Provides translation services for array fragments.
+    /// </summary>
+    public class NpgsqlArrayFragmentTranslator : IExpressionFragmentTranslator
+    {
+        #region MethodInfoFields
+
+        /// <summary>
+        /// The <see cref="MethodInfo"/> for <see cref="DbFunctionsExtensions.Like(DbFunctions,string,string)"/>.
+        /// </summary>
+        [NotNull] static readonly MethodInfo Like2MethodInfo =
+            typeof(DbFunctionsExtensions)
+                .GetRuntimeMethod(nameof(DbFunctionsExtensions.Like), new[] { typeof(DbFunctions), typeof(string), typeof(string) });
+
+        /// <summary>
+        /// The <see cref="MethodInfo"/> for <see cref="DbFunctionsExtensions.Like(DbFunctions,string,string, string)"/>.
+        /// </summary>
+        [NotNull] static readonly MethodInfo Like3MethodInfo =
+            typeof(DbFunctionsExtensions)
+                .GetRuntimeMethod(nameof(DbFunctionsExtensions.Like), new[] { typeof(DbFunctions), typeof(string), typeof(string), typeof(string) });
+
+        // ReSharper disable once InconsistentNaming
+        /// <summary>
+        /// The <see cref="MethodInfo"/> for <see cref="NpgsqlDbFunctionsExtensions.ILike(DbFunctions,string,string)"/>.
+        /// </summary>
+        [NotNull] static readonly MethodInfo ILike2MethodInfo =
+            typeof(NpgsqlDbFunctionsExtensions)
+                .GetRuntimeMethod(nameof(NpgsqlDbFunctionsExtensions.ILike), new[] { typeof(DbFunctions), typeof(string), typeof(string) });
+
+        // ReSharper disable once InconsistentNaming
+        /// <summary>
+        /// The <see cref="MethodInfo"/> for <see cref="NpgsqlDbFunctionsExtensions.ILike(DbFunctions,string,string,string)"/>.
+        /// </summary>
+        [NotNull] static readonly MethodInfo ILike3MethodInfo =
+            typeof(NpgsqlDbFunctionsExtensions)
+                .GetRuntimeMethod(nameof(NpgsqlDbFunctionsExtensions.ILike), new[] { typeof(DbFunctions), typeof(string), typeof(string), typeof(string) });
+
+        #endregion
+
+        /// <inheritdoc />
+        [CanBeNull]
+        public Expression Translate(Expression expression)
+        {
+            if (!(expression is SubQueryExpression subQuery))
+                return null;
+
+            var model = subQuery.QueryModel;
+
+            if (!IsArrayOrList(model.MainFromClause.FromExpression.Type))
+                return null;
+
+            return
+                AllResult(model) ??
+                AnyResult(model) ??
+                ConcatResult(model) ??
+                CountResult(model);
+        }
+
+        #region SubQueries
+
+        /// <summary>
+        /// Visits an array-based ALL expression.
+        /// </summary>
+        /// <param name="model">The query model to visit.</param>
+        /// <returns>
+        /// An expression or null.
+        /// </returns>
+        [CanBeNull]
+        static Expression AllResult([NotNull] QueryModel model)
+        {
+            Expression array = model.MainFromClause.FromExpression;
+
+            // TODO: when is there more than one result operator?
+            // Only handle singular result operators.
+            if (model.ResultOperators.Count == 1 && model.ResultOperators[0] is AllResultOperator all)
+                return ConstructArrayLike(array, all.Predicate, ArrayComparisonType.ALL);
+
+            return null;
+        }
+
+        /// <summary>
+        /// Visits an array-based ANY expression.
+        /// </summary>
+        /// <param name="model">The query model to visit.</param>
+        /// <returns>
+        /// An expression or null.
+        /// </returns>
+        [CanBeNull]
+        static Expression AnyResult([NotNull] QueryModel model)
+        {
+            Expression array = model.MainFromClause.FromExpression;
+
+            // TODO: when is there more than one result operator?
+            // Only handle singular result operators.
+            if (model.ResultOperators.Count != 1 || !(model.ResultOperators[0] is AnyResultOperator _))
+                return null;
+
+            if (model.BodyClauses.Count == 1 && model.BodyClauses[0] is WhereClause where)
+                return ConstructArrayLike(array, where.Predicate, ArrayComparisonType.ANY);
+
+            return null;
+        }
+
+        /// <summary>
+        /// Visits an array-based concatenation expression: {array|value} || {array|value}.
+        /// </summary>
+        /// <param name="model">The query model to visit.</param>
+        /// <returns>
+        /// An expression or null.
+        /// </returns>
+        [CanBeNull]
+        static Expression ConcatResult([NotNull] QueryModel model)
+        {
+            if (model.BodyClauses.Count != 0)
+                return null;
+
+            if (model.ResultOperators.Count != 1)
+                return null;
+
+            if (!(model.ResultOperators[0] is ConcatResultOperator concat))
+                return null;
+
+            Expression from = model.MainFromClause.FromExpression;
+
+            Expression other = concat.Source2;
+
+            if (!IsArrayOrList(other.Type))
+                return null;
+
+            return new CustomBinaryExpression(from, other, "||", from.Type);
+        }
+
+        /// <summary>
+        /// Visits an array-based count expression: {array}.Length, {list}.Count, {array|list}.Count(), {array|list}.Count({predicate}).
+        /// </summary>
+        /// <param name="model">The query model to visit.</param>
+        /// <returns>
+        /// An expression or null.
+        /// </returns>
+        [CanBeNull]
+        static Expression CountResult([NotNull] QueryModel model)
+        {
+            // TODO: handle count operation with predicate.
+            if (model.BodyClauses.Count != 0)
+                return null;
+
+            if (model.ResultOperators.Count != 1)
+                return null;
+
+            if (!(model.ResultOperators[0] is CountResultOperator _))
+                return null;
+
+            Expression from = model.MainFromClause.FromExpression;
+
+            return
+                from.Type.IsArray
+                    ? Expression.MakeMemberAccess(from, from.Type.GetRuntimeProperty(nameof(Array.Length)))
+                    : Expression.MakeMemberAccess(from, from.Type.GetRuntimeProperty(nameof(IList.Count)));
+        }
+
+        /// <summary>
+        /// Visits an array-based comparison for an LIKE or ILIKE expression: {operand} {LIKE|ILIKE} {ANY|ALL} ({array}).
+        /// </summary>
+        /// <param name="array">The array expression.</param>
+        /// <param name="predicate">The method call expression.</param>
+        /// <param name="comparisonType">The array comparison type.</param>
+        /// <returns>
+        /// An expression or null.
+        /// </returns>
+        [CanBeNull]
+        static Expression ConstructArrayLike([NotNull] Expression array, [CanBeNull] Expression predicate, ArrayComparisonType comparisonType)
+        {
+            if (!(predicate is MethodCallExpression call))
+                return null;
+
+            if (call.Arguments.Count < 2)
+                return null;
+
+            Expression operand = call.Arguments[1];
+            Expression collection = array;
+
+            switch (call.Method)
+            {
+            case MethodInfo m when m == Like2MethodInfo:
+                return new ArrayAnyAllExpression(comparisonType, "LIKE", operand, collection);
+
+            case MethodInfo m when m == Like3MethodInfo:
+                return new ArrayAnyAllExpression(comparisonType, "LIKE", operand, collection);
+
+            case MethodInfo m when m == ILike2MethodInfo:
+                return new ArrayAnyAllExpression(comparisonType, "ILIKE", operand, collection);
+
+            case MethodInfo m when m == ILike3MethodInfo:
+                return new ArrayAnyAllExpression(comparisonType, "ILIKE", operand, collection);
+
+            default:
+                return null;
+            }
+        }
+
+        #endregion
+
+        #region Helpers
+
+        /// <summary>
+        /// Tests if the type is an array or a <see cref="List{T}"/>.
+        /// </summary>
+        /// <param name="type">The type to test.</param>
+        /// <returns>
+        /// True if <paramref name="type"/> is an array or a <see cref="List{T}"/>; otherwise, false.
+        /// </returns>
+        static bool IsArrayOrList([NotNull] Type type) => type.IsArray || type.IsGenericType && type.GetGenericTypeDefinition() == typeof(List<>);
+
+        #endregion
+    }
+}

src/EFCore.PG/Query/ExpressionTranslators/Internal/NpgsqlArrayMemberTranslator.cs

@@ -0,0 +1,112 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq.Expressions;
+using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore.Query.Expressions;
+using Microsoft.EntityFrameworkCore.Query.ExpressionTranslators;
+
+namespace Npgsql.EntityFrameworkCore.PostgreSQL.Query.ExpressionTranslators.Internal
+{
+    /// <summary>
+    /// Provides translation services for PostgreSQL array operators mapped to generic array members.
+    /// </summary>
+    /// <remarks>
+    /// See: https://www.postgresql.org/docs/current/static/functions-array.html
+    /// </remarks>
+    public class NpgsqlArrayMemberTranslator : IMemberTranslator
+    {
+        /// <summary>
+        /// The backend version to target.
+        /// </summary>
+        [CanBeNull] readonly Version _postgresVersion;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="NpgsqlArrayMemberTranslator"/> class.
+        /// </summary>
+        /// <param name="postgresVersion">The backend version to target.</param>
+        public NpgsqlArrayMemberTranslator([CanBeNull] Version postgresVersion) => _postgresVersion = postgresVersion;
+
+        /// <inheritdoc />
+        public Expression Translate(MemberExpression e)
+        {
+            if (!VersionAtLeast(9, 4))
+                return null;
+
+            return ArrayInstanceHandler(e) ??
+                   ListInstanceHandler(e);
+        }
+
+        #region Handlers
+
+        [CanBeNull]
+        static Expression ArrayInstanceHandler([NotNull] MemberExpression e)
+        {
+            var instance = e.Expression;
+
+            if (instance == null || !instance.Type.IsArray || instance.Type.GetArrayRank() != 1)
+                return null;
+
+            switch (e.Member.Name)
+            {
+            case nameof(Array.Length):
+                return Expression.Coalesce(
+                    new SqlFunctionExpression(
+                        "array_length",
+                        typeof(int?),
+                        new[] { instance, Expression.Constant(1) }),
+                    Expression.Constant(0));
+
+            case nameof(Array.Rank):
+                return Expression.Coalesce(
+                    new SqlFunctionExpression(
+                        "array_ndims",
+                        typeof(int?),
+                        new[] { instance }),
+                    Expression.Constant(1));
+
+            default:
+                return null;
+            }
+        }
+
+        [CanBeNull]
+        static Expression ListInstanceHandler([NotNull] MemberExpression e)
+        {
+            var instance = e.Expression;
+
+            if (instance is null || !instance.Type.IsGenericType || instance.Type.GetGenericTypeDefinition() != typeof(List<>))
+                return null;
+
+            switch (e.Member.Name)
+            {
+            case nameof(IList.Count):
+                return Expression.Coalesce(
+                    new SqlFunctionExpression(
+                        "array_length",
+                        typeof(int?),
+                        new Expression[] { instance, Expression.Constant(1) }),
+                    Expression.Constant(0));
+
+            default:
+                return null;
+            }
+        }
+
+        #endregion
+
+        #region Helpers
+
+        /// <summary>
+        /// True if <see cref="_postgresVersion"/> is null, greater than, or equal to the specified version.
+        /// </summary>
+        /// <param name="major">The major version.</param>
+        /// <param name="minor">The minor version.</param>
+        /// <returns>
+        /// True if <see cref="_postgresVersion"/> is null, greater than, or equal to the specified version.
+        /// </returns>
+        bool VersionAtLeast(int major, int minor) => _postgresVersion is null || new Version(major, minor) <= _postgresVersion;
+
+        #endregion
+    }
+}