Fix to #26676 - EF Core 6 - IsTemporal adds an unnecessary migration …

…when DefaultSchema is configured at the DbContext Level

Problem was a discrepancy between RelationalModel build in runtime and the current model (from OnModelCreating) - relational model would set history table schema annotation using the table schema or default schema, however current model wouldn't set those annotations.
Model differ would then pick up on those differences and create migration to set the schema for history table. When building actual migration sql we already compensated for the difference and not generate actual sql code, but the problem persists.

Fix is to improve the temporal convention so that history table schema in current model (more) closely resembles the temporal table schema and therefore is similar to RelationalModel generated in runtime.

Fixes #26676

src/EFCore.SqlServer/Extensions/SqlServerEntityTypeExtensions.cs

@@ -16,8 +16,6 @@ namespace Microsoft.EntityFrameworkCore;
 /// </remarks>
 public static class SqlServerEntityTypeExtensions
 {
-    private const string DefaultHistoryTableNameSuffix = "History";
-
     /// <summary>
     ///     Returns a value indicating whether the entity type is mapped to a memory-optimized table.
     /// </summary>
@@ -202,11 +200,7 @@ public static void SetPeriodEndPropertyName(this IMutableEntityType entityType,
             ? throw new InvalidOperationException(CoreStrings.RuntimeModelMissingData)
             : entityType[SqlServerAnnotationNames.TemporalHistoryTableName] is string historyTableName
                 ? historyTableName
-                : entityType[SqlServerAnnotationNames.IsTemporal] as bool? == true
-                    ? entityType.GetTableName() is string tableName
-                        ? tableName + DefaultHistoryTableNameSuffix
-                        : null
-                    : null;
+                : null;
 
     /// <summary>
     ///     Sets a value representing the name of the history table associated with the entity mapped to a temporal table.
@@ -252,8 +246,7 @@ public static void SetHistoryTableName(this IMutableEntityType entityType, strin
     public static string? GetHistoryTableSchema(this IReadOnlyEntityType entityType)
         => (entityType is RuntimeEntityType)
             ? throw new InvalidOperationException(CoreStrings.RuntimeModelMissingData)
-            : entityType[SqlServerAnnotationNames.TemporalHistoryTableSchema] as string
-            ?? entityType[RelationalAnnotationNames.Schema] as string;
+            : entityType[SqlServerAnnotationNames.TemporalHistoryTableSchema] as string;
 
     /// <summary>
     ///     Sets a value representing the schema of the history table associated with the entity mapped to a temporal table.

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

@@ -15,8 +15,9 @@ namespace Microsoft.EntityFrameworkCore.Metadata.Conventions;
 /// </remarks>
 public class SqlServerTemporalConvention : IEntityTypeAnnotationChangedConvention, ISkipNavigationForeignKeyChangedConvention
 {
-    private const string PeriodStartDefaultName = "PeriodStart";
-    private const string PeriodEndDefaultName = "PeriodEnd";
+    private const string DefaultPeriodStartName = "PeriodStart";
+    private const string DefaultPeriodEndName = "PeriodEnd";
+    private const string DefaultHistoryTableNameSuffix = "History";
 
     /// <summary>
     ///     Creates a new instance of <see cref="SqlServerTemporalConvention" />.
@@ -56,12 +57,18 @@ public virtual void ProcessEntityTypeAnnotationChanged(
             {
                 if (entityTypeBuilder.Metadata.GetPeriodStartPropertyName() == null)
                 {
-                    entityTypeBuilder.HasPeriodStart(PeriodStartDefaultName);
+                    entityTypeBuilder.HasPeriodStart(DefaultPeriodStartName);
                 }
 
                 if (entityTypeBuilder.Metadata.GetPeriodEndPropertyName() == null)
                 {
-                    entityTypeBuilder.HasPeriodEnd(PeriodEndDefaultName);
+                    entityTypeBuilder.HasPeriodEnd(DefaultPeriodEndName);
+                }
+
+                if (entityTypeBuilder.Metadata.GetHistoryTableName() == null)
+                {
+                    var tableName = entityTypeBuilder.Metadata.GetTableName();
+                    entityTypeBuilder.UseHistoryTableName(tableName + DefaultHistoryTableNameSuffix);
                 }
 
                 foreach (var skipLevelNavigation in entityTypeBuilder.Metadata.GetSkipNavigations())
@@ -118,6 +125,23 @@ public virtual void ProcessEntityTypeAnnotationChanged(
                 periodPropertyBuilder?.HasColumnName(periodPropertyName);
             }
         }
+
+        if (name == RelationalAnnotationNames.Schema
+            && entityTypeBuilder.Metadata.IsTemporal())
+        {
+            // if table schema changes, also update the history table schema
+            entityTypeBuilder.UseHistoryTableSchema(annotation?.Value as string);
+        }
+
+        if (name == SqlServerAnnotationNames.TemporalHistoryTableName)
+        {
+            // when setting up history table (name),
+            // also by convention set up it's schema to be the same as the temporal table
+            // we have to use annotation directly, so that we don't use the default model schema
+            // in case table schema is not explicitly set
+            var tableSchemaAnnotation = entityTypeBuilder.Metadata.FindAnnotation(RelationalAnnotationNames.Schema);
+            entityTypeBuilder.UseHistoryTableSchema(tableSchemaAnnotation?.Value as string);
+        }
     }
 
     /// <inheritdoc />

src/EFCore.SqlServer/Migrations/SqlServerMigrationsSqlGenerator.cs

@@ -533,7 +533,8 @@ protected override void Generate(
         if (operation[SqlServerAnnotationNames.IsTemporal] as bool? == true)
         {
             var historyTableSchema = operation[SqlServerAnnotationNames.TemporalHistoryTableSchema] as string
-                ?? model?.GetDefaultSchema();
+                ?? operation.Schema;
+
             var needsExec = historyTableSchema == null;
             var subBuilder = needsExec
                 ? new MigrationCommandListBuilder(Dependencies)
@@ -1261,7 +1262,7 @@ protected override void Generate(
         {
             var historyTableName = operation[SqlServerAnnotationNames.TemporalHistoryTableName] as string;
             var historyTableSchema = operation[SqlServerAnnotationNames.TemporalHistoryTableSchema] as string
-                ?? model?.GetDefaultSchema();
+                ?? operation.Schema ?? model?.GetDefaultSchema();
             var periodStartColumnName = operation[SqlServerAnnotationNames.TemporalPeriodStartColumnName] as string;
             var periodEndColumnName = operation[SqlServerAnnotationNames.TemporalPeriodEndColumnName] as string;
 
@@ -2261,7 +2262,7 @@ private IReadOnlyList<MigrationOperation> RewriteOperations(
                 schema ??= model?.GetDefaultSchema();
                 var historyTableName = operation[SqlServerAnnotationNames.TemporalHistoryTableName] as string;
                 var historyTableSchema = operation[SqlServerAnnotationNames.TemporalHistoryTableSchema] as string
-                    ?? model?.GetDefaultSchema();
+                    ?? schema;
                 var periodStartColumnName = operation[SqlServerAnnotationNames.TemporalPeriodStartColumnName] as string;
                 var periodEndColumnName = operation[SqlServerAnnotationNames.TemporalPeriodEndColumnName] as string;