query part

- query apis for temporal operations
- query root creator service that can now construct query root expressions in nav expansion

tests for now are simply converted exisiting tests
- used the original model & data
- map entities to temporal in the model configuration
- modify the data (remove or change values),
- manually change the history table to make history deterministic (rather than based on current date),
- added visitor to inject temporal operation to every query, which "time travels" to before the modifications above were made, so we should still get the same results as non-temporal & not modified data

src/EFCore.SqlServer/Extensions/SqlServerQueryableExtensions.cs

@@ -0,0 +1,211 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Linq;
+using System.Linq.Expressions;
+using Microsoft.EntityFrameworkCore.Query;
+using Microsoft.EntityFrameworkCore.SqlServer.Query.Internal;
+using Microsoft.EntityFrameworkCore.Utilities;
+
+// ReSharper disable once CheckNamespace
+namespace Microsoft.EntityFrameworkCore
+{
+    /// <summary>
+    ///     Sql Server database specific extension methods for LINQ queries.
+    /// </summary>
+    public static class SqlServerQueryableExtensions
+    {
+        /// <summary>
+        ///     <para>
+        ///         Applies temporal 'AsOf' operation on the given DbSet, which only returns elements that were present in the database at a given point in time.
+        ///     </para>
+        ///     <para>
+        ///         Temporal queries are always set as 'NoTracking'.
+        ///     </para>
+        /// </summary>
+        /// <param name="source">Source DbSet on which the temporal operation is applied.</param>
+        /// <param name="pointInTime"><see cref="DateTime" /> representing a point in time for which the results should be returned.</param>
+        /// <returns> An <see cref="IQueryable{T}" /> representing the entities at a given point in time.</returns>
+        public static IQueryable<TEntity> TemporalAsOf<TEntity>(
+            this DbSet<TEntity> source,
+            DateTime pointInTime)
+            where TEntity : class
+        {
+            Check.NotNull(source, nameof(source));
+
+            var queryableSource = (IQueryable)source;
+
+            return queryableSource.Provider.CreateQuery<TEntity>(
+                GenerateTemporalAsOfQueryRoot<TEntity>(
+                    queryableSource,
+                    pointInTime)).AsNoTracking();
+        }
+
+        /// <summary>
+        ///     <para>
+        ///         Applies temporal 'FromTo' operation on the given DbSet, which only returns elements that were present in the database between two points in time. 
+        ///     </para>
+        ///     <para>
+        ///         Elements that were created at the starting point as well as elements that were removed at the end point are not included in the results.
+        ///     </para>
+        ///     <para>
+        ///         All versions of entities in that were present within the time range are returned, so it is possible to return multiple entities with the same key.
+        ///     </para>
+        ///     <para>
+        ///         Temporal queries are always set as 'NoTracking'.
+        ///     </para>
+        /// </summary>
+        /// <param name="source">Source DbSet on which the temporal operation is applied.</param>
+        /// <param name="from">Point in time representing the start of the period for which results should be returned.</param>
+        /// <param name="to">Point in time representing the end of the period for which results should be returned.</param>
+        /// <returns> An <see cref="IQueryable{T}" /> representing the entities present in a given time range.</returns>
+        public static IQueryable<TEntity> TemporalFromTo<TEntity>(
+            this DbSet<TEntity> source,
+            DateTime from,
+            DateTime to)
+            where TEntity : class
+        {
+            Check.NotNull(source, nameof(source));
+
+            var queryableSource = (IQueryable)source;
+
+            return queryableSource.Provider.CreateQuery<TEntity>(
+                GenerateRangeTemporalQueryRoot<TEntity>(
+                    queryableSource,
+                    from,
+                    to,
+                    TemporalOperationType.FromTo)).AsNoTracking();
+        }
+
+        /// <summary>
+        ///     <para>
+        ///         Applies temporal 'Between' operation on the given DbSet, which only returns elements that were present in the database between two points in time. 
+        ///     </para>
+        ///     <para>
+        ///         Elements that were created at the starting point are not included in the results, however elements that were removed at the end point are included in the results.
+        ///     </para>
+        ///     <para>
+        ///         All versions of entities in that were present within the time range are returned, so it is possible to return multiple entities with the same key.
+        ///     </para>
+        ///     <para>
+        ///         Temporal queries are always set as 'NoTracking'.
+        ///     </para>
+        /// </summary>
+        /// <param name="source">Source DbSet on which the temporal operation is applied.</param>
+        /// <param name="from">Point in time representing the start of the period for which results should be returned.</param>
+        /// <param name="to">Point in time representing the end of the period for which results should be returned.</param>
+        /// <returns> An <see cref="IQueryable{T}" /> representing the entities present in a given time range.</returns>
+        public static IQueryable<TEntity> TemporalBetween<TEntity>(
+            this IQueryable<TEntity> source,
+            DateTime from,
+            DateTime to)
+            where TEntity : class
+        {
+            Check.NotNull(source, nameof(source));
+
+            var queryableSource = (IQueryable)source;
+
+            return queryableSource.Provider.CreateQuery<TEntity>(
+                GenerateRangeTemporalQueryRoot<TEntity>(
+                    queryableSource,
+                    from,
+                    to,
+                    TemporalOperationType.Between)).AsNoTracking();
+        }
+
+        /// <summary>
+        ///     <para>
+        ///         Applies temporal 'ContainedIn' operation on the given DbSet, which only returns elements that were present in the database between two points in time. 
+        ///     </para>
+        ///     <para>
+        ///         Elements that were created at the starting point as well as elements that were removed at the end point are included in the results.
+        ///     </para>
+        ///     <para>
+        ///         All versions of entities in that were present within the time range are returned, so it is possible to return multiple entities with the same key.
+        ///     </para>
+        ///     <para>
+        ///         Temporal queries are always set as 'NoTracking'.
+        ///     </para>
+        /// </summary>
+        /// <param name="source">Source DbSet on which the temporal operation is applied.</param>
+        /// <param name="from">Point in time representing the start of the period for which results should be returned.</param>
+        /// <param name="to">Point in time representing the end of the period for which results should be returned.</param>
+        /// <returns> An <see cref="IQueryable{T}" /> representing the entities present in a given time range.</returns>
+        public static IQueryable<TEntity> TemporalContainedIn<TEntity>(
+            this DbSet<TEntity> source,
+            DateTime from,
+            DateTime to)
+            where TEntity : class
+        {
+            Check.NotNull(source, nameof(source));
+
+            var queryableSource = (IQueryable)source;
+
+            return queryableSource.Provider.CreateQuery<TEntity>(
+                GenerateRangeTemporalQueryRoot<TEntity>(
+                    queryableSource,
+                    from,
+                    to,
+                    TemporalOperationType.ContainedIn)).AsNoTracking();
+        }
+
+        /// <summary>
+        ///     <para>
+        ///         Applies temporal 'All' operation on the given DbSet, which returns all historical versions of the entities as well as their current state. 
+        ///     </para>
+        ///     <para>
+        ///         Temporal queries are always set as 'NoTracking'.
+        ///     </para>
+        /// </summary>
+        /// <param name="source">Source DbSet on which the temporal operation is applied.</param>
+        /// <returns> An <see cref="IQueryable{T}" /> representing the entities and their historical versions.</returns>
+        public static IQueryable<TEntity> TemporalAll<TEntity>(
+            this DbSet<TEntity> source)
+            where TEntity : class
+        {
+            Check.NotNull(source, nameof(source));
+
+            var queryableSource = (IQueryable)source;
+            var queryRootExpression = (QueryRootExpression)queryableSource.Expression;
+            var entityType = queryRootExpression.EntityType;
+
+            var temporalQueryRootExpression = new TemporalAllQueryRootExpression(
+                queryRootExpression.QueryProvider!,
+                entityType);
+
+            return queryableSource.Provider.CreateQuery<TEntity>(temporalQueryRootExpression)
+                .AsNoTracking();
+        }
+
+        private static Expression GenerateTemporalAsOfQueryRoot<TEntity>(
+            IQueryable source,
+            DateTime pointInTime)
+        {
+            var queryRootExpression = (QueryRootExpression)source.Expression;
+            var entityType = queryRootExpression.EntityType;
+
+            return new TemporalAsOfQueryRootExpression(
+                queryRootExpression.QueryProvider!,
+                entityType,
+                pointInTime: pointInTime);
+        }
+
+        private static Expression GenerateRangeTemporalQueryRoot<TEntity>(
+            IQueryable source,
+            DateTime from,
+            DateTime to,
+            TemporalOperationType temporalOperationType)
+        {
+            var queryRootExpression = (QueryRootExpression)source.Expression;
+            var entityType = queryRootExpression.EntityType;
+
+            return new TemporalRangeQueryRootExpression(
+                queryRootExpression.QueryProvider!,
+                entityType,
+                from: from,
+                to: to,
+                temporalOperationType: temporalOperationType);
+        }
+    }
+}

src/EFCore.SqlServer/Extensions/SqlServerServiceCollectionExtensions.cs

@@ -79,6 +79,8 @@ public static IServiceCollection AddEntityFrameworkSqlServer(this IServiceCollec
                 .TryAdd<IQuerySqlGeneratorFactory, SqlServerQuerySqlGeneratorFactory>()
                 .TryAdd<IRelationalSqlTranslatingExpressionVisitorFactory, SqlServerSqlTranslatingExpressionVisitorFactory>()
                 .TryAdd<IRelationalParameterBasedSqlProcessorFactory, SqlServerParameterBasedSqlProcessorFactory>()
+                .TryAdd<IQueryRootCreator, SqlServerQueryRootCreator>()
+                .TryAdd<IQueryableMethodTranslatingExpressionVisitorFactory, SqlServerQueryableMethodTranslatingExpressionVisitorFactory>()
                 .TryAddProviderSpecificServices(
                     b => b
                         .TryAddSingleton<ISqlServerValueGeneratorCache, SqlServerValueGeneratorCache>()

src/EFCore.SqlServer/Metadata/Conventions/SqlServerConventionSetBuilder.cs

@@ -64,9 +64,10 @@ public override ConventionSet CreateConventionSet()
             ReplaceConvention(
                 conventionSet.EntityTypeAnnotationChangedConventions, (RelationalValueGenerationConvention)valueGenerationConvention);
 
+            var sqlServerTemporalConvention = new SqlServerTemporalConvention();
             ConventionSet.AddBefore(
                 conventionSet.EntityTypeAnnotationChangedConventions,
-                new SqlServerTemporalConvention(),
+                sqlServerTemporalConvention,
                 typeof(SqlServerValueGenerationConvention));
 
             ReplaceConvention(conventionSet.EntityTypePrimaryKeyChangedConventions, valueGenerationConvention);
@@ -110,6 +111,8 @@ public override ConventionSet CreateConventionSet()
                 conventionSet.ModelFinalizedConventions,
                 (RuntimeModelConvention)new SqlServerRuntimeModelConvention(Dependencies, RelationalDependencies));
 
+            conventionSet.SkipNavigationForeignKeyChangedConventions.Add(sqlServerTemporalConvention);
+
             return conventionSet;
         }
 

src/EFCore.SqlServer/Metadata/Conventions/SqlServerTemporalConvention.cs

@@ -10,7 +10,7 @@ namespace Microsoft.EntityFrameworkCore.Metadata.Conventions
     /// <summary>
     ///     A convention that manipulates temporal settings for an entity mapped to a temporal table.
     /// </summary>
-    public class SqlServerTemporalConvention : IEntityTypeAnnotationChangedConvention
+    public class SqlServerTemporalConvention : IEntityTypeAnnotationChangedConvention, ISkipNavigationForeignKeyChangedConvention
     {
         private const string PeriodStartDefaultName = "PeriodStart";
         private const string PeriodEndDefaultName = "PeriodEnd";
@@ -81,5 +81,24 @@ public virtual void ProcessEntityTypeAnnotationChanged(
                 }
             }
         }
+
+        /// <inheritdoc />
+        public virtual void ProcessSkipNavigationForeignKeyChanged(
+            IConventionSkipNavigationBuilder skipNavigationBuilder,
+            IConventionForeignKey? foreignKey,
+            IConventionForeignKey? oldForeignKey,
+            IConventionContext<IConventionForeignKey> context)
+        {
+             if (skipNavigationBuilder.Metadata.JoinEntityType is IConventionEntityType joinEntityType
+                && joinEntityType.HasSharedClrType
+                && !joinEntityType.IsTemporal()
+                && joinEntityType.GetConfigurationSource() == ConfigurationSource.Convention
+                && skipNavigationBuilder.Metadata.DeclaringEntityType.IsTemporal()
+                && skipNavigationBuilder.Metadata.Inverse is IConventionSkipNavigation inverse
+                && inverse.DeclaringEntityType.IsTemporal())
+            {
+                joinEntityType.SetIsTemporal(true);
+            }
+        }
     }
 }

src/EFCore.SqlServer/Properties/SqlServerStrings.resx

@@ -319,4 +319,16 @@
     <value>Property '{entityType}.{propertyName}' is mapped to the period column and can't have default value specified.</value>
   </data>
 
+  <data name="TemporalNavigationExpansionBetweenTemporalAndNonTemporal" xml:space="preserve">
+    <value>Temporal query is trying to use navigation to an entity '{entityType}' which itself doesn't map to temporal table. Either map the entity to temporal table or use join manually to access it.</value>
+  </data>
+
+  <data name="TemporalNavigationExpansionOnlySupportedForAsOf" xml:space="preserve">
+    <value>Navigation expansion is only supported for '{operationName}' temporal operation. For other operations use join manually.</value>
+  </data>
+
+  <data name="TemporalSetOperationOnMismatchedSources" xml:space="preserve">
+    <value>Set operation can't be applied on entity '{entityType}' because temporal operations on both arguments don't match.</value>
+  </data>
+
 </root>

src/EFCore.SqlServer/Query/Internal/SqlServerParameterBasedSqlProcessor.cs

@@ -53,5 +53,21 @@ public override SelectExpression Optimize(
             return (SelectExpression)new SearchConditionConvertingExpressionVisitor(Dependencies.SqlExpressionFactory)
                 .Visit(optimizedSelectExpression);
         }
+
+        /// <summary>
+        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+        ///     any release. You should only use it directly in your code with extreme caution and knowing that
+        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
+        /// </summary>
+        protected override SelectExpression ProcessSqlNullability(
+            SelectExpression selectExpression,
+            IReadOnlyDictionary<string, object?> parametersValues, out bool canCache)
+        {
+            Check.NotNull(selectExpression, nameof(selectExpression));
+            Check.NotNull(parametersValues, nameof(parametersValues));
+
+            return new SqlServerSqlNullabilityProcessor(Dependencies, UseRelationalNulls).Process(selectExpression, parametersValues, out canCache);
+        }
     }
 }