From 51c0bee90433c8c717f2891eb5c5bcc5c4548323 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philippe=20L=C3=A9caillon?= <lecaillon@hotmail.com>
Date: Fri, 23 Feb 2018 21:05:29 +0100
Subject: [PATCH] #36 Support to drop temporal tables in SQL Server.

---
 .../Dialect/SQLServer/SQLServerSchema.cs      | 55 ++++++++++++++++---
 src/Evolve/Evolve.nuspec                      |  1 +
 .../Migration/V2_1__create_table_test.sql     | 16 +++++-
 3 files changed, 62 insertions(+), 10 deletions(-)

diff --git a/src/Evolve/Dialect/SQLServer/SQLServerSchema.cs b/src/Evolve/Dialect/SQLServer/SQLServerSchema.cs
index 5dd5c722..cbe5adee 100644
--- a/src/Evolve/Dialect/SQLServer/SQLServerSchema.cs
+++ b/src/Evolve/Dialect/SQLServer/SQLServerSchema.cs
@@ -1,10 +1,13 @@
-using System.Linq;
+using System;
+using System.Linq;
 using Evolve.Connection;
 
 namespace Evolve.Dialect.SQLServer
 {
     public class SQLServerSchema : Schema
     {
+        private long _version = 0;
+
         public SQLServerSchema(string schemaName, WrappedConnection wrappedConnection) : base(schemaName, wrappedConnection)
         {
         }
@@ -54,11 +57,12 @@ public override bool Erase()
             DropDefaultConstraints();
             DropProcedures();
             DropViews();
+            DropSystemVersioning();  // SQLServerVersion >= 13
             DropTables();
             DropFunctions();
             DropTypes();
             DropSynonyms();
-            DropSequences(); // SQLServer >= 11
+            DropSequences(); // SQLServerVersion >= 11
 
             return true;
         }
@@ -108,6 +112,25 @@ protected void DropViews()
             });
         }
 
+        private void DropSystemVersioning()
+        {
+            if (SQLServerVersion < 13)
+            {
+                return;
+            }
+
+            string sql = "SELECT t.name as TABLE_NAME " +
+                         "FROM sys.tables t " +
+                         "INNER JOIN sys.schemas s ON s.schema_id = t.schema_id " +
+                        $"WHERE s.name = '{Name}' " +
+                         "AND t.temporal_type = 2";
+
+            _wrappedConnection.QueryForListOfString(sql).ToList().ForEach(table =>
+            {
+                _wrappedConnection.ExecuteNonQuery($"ALTER TABLE [{Name}].[{table}] SET (SYSTEM_VERSIONING = OFF)");
+            });
+        }
+
         protected void DropTables()
         {
             string sql = $"SELECT table_name FROM INFORMATION_SCHEMA.TABLES WHERE table_type='BASE TABLE' AND table_schema = '{Name}'";
@@ -146,14 +169,10 @@ protected void DropSynonyms()
 
         protected void DropSequences()
         {
-            string sqlversion = "SELECT CAST (CASE WHEN CAST(SERVERPROPERTY ('productversion') as VARCHAR) LIKE '8%' THEN 8 " +
-                                                  "WHEN CAST(SERVERPROPERTY ('productversion') as VARCHAR) LIKE '9%' THEN 9 " +
-                                                  "WHEN CAST(SERVERPROPERTY ('productversion') as VARCHAR) LIKE '10%' THEN 10 " +
-                                                  "ELSE CAST(LEFT(CAST(SERVERPROPERTY ('productversion') as VARCHAR), 2) as int) " +
-                                             "END AS int)";
-
-            if (_wrappedConnection.QueryForLong(sqlversion) < 11)
+            if (SQLServerVersion < 11)
+            {
                 return;
+            }
 
             string sql = $"SELECT sequence_name FROM INFORMATION_SCHEMA.SEQUENCES WHERE sequence_schema = '{Name}'";
             _wrappedConnection.QueryForListOfString(sql).ToList().ForEach(s =>
@@ -161,5 +180,23 @@ protected void DropSequences()
                 _wrappedConnection.ExecuteNonQuery($"DROP SEQUENCE [{Name}].[{s}]");
             });
         }
+
+        private long SQLServerVersion
+        {
+            get
+            {
+                if (_version > 0)
+                {
+                    return _version;
+                }
+
+                _version = _wrappedConnection.QueryForLong("SELECT CAST (CASE WHEN CAST(SERVERPROPERTY ('productversion') as VARCHAR) LIKE '8%' THEN 8 " +
+                                                                             "WHEN CAST(SERVERPROPERTY ('productversion') as VARCHAR) LIKE '9%' THEN 9 " +
+                                                                             "WHEN CAST(SERVERPROPERTY ('productversion') as VARCHAR) LIKE '10%' THEN 10 " +
+                                                                             "ELSE CAST(LEFT(CAST(SERVERPROPERTY ('productversion') as VARCHAR), 2) as int) " +
+                                                                        "END AS int)");
+                return _version;
+            }
+        }
     }
 }
diff --git a/src/Evolve/Evolve.nuspec b/src/Evolve/Evolve.nuspec
index fd509b3f..b5aef85b 100644
--- a/src/Evolve/Evolve.nuspec
+++ b/src/Evolve/Evolve.nuspec
@@ -15,6 +15,7 @@ Every time you build your project, it will automatically ensure that your databa
     <releaseNotes>- Full .NET Core 2.0 support.
 - Add a new configuration parameter: Evolve.CommandTimeout.
 - Normalize line endings when calculating checksums. (Thx to @mhelleborg)
+- Support to drop temporal tables in SQL Server.
 - New Cake build script.
 - Add new Evolve package integration tests.
 - Fix Linux evolve.json not found for lowercase file name.
diff --git a/test/Evolve.IntegrationTest.SQLServer/Resources/Sql_Scripts/Migration/V2_1__create_table_test.sql b/test/Evolve.IntegrationTest.SQLServer/Resources/Sql_Scripts/Migration/V2_1__create_table_test.sql
index 870ade60..0f86b2a0 100644
--- a/test/Evolve.IntegrationTest.SQLServer/Resources/Sql_Scripts/Migration/V2_1__create_table_test.sql
+++ b/test/Evolve.IntegrationTest.SQLServer/Resources/Sql_Scripts/Migration/V2_1__create_table_test.sql
@@ -6,4 +6,18 @@ CREATE TABLE TEST
 	DATE_TEST							date	NOT NULL,
 
 	FOREIGN KEY (DATE_TEST) REFERENCES CALENDRIER (JOUR) ON DELETE CASCADE,
-)
\ No newline at end of file
+);
+
+CREATE TABLE dbo.Employee   
+(    
+  [EmployeeID] int NOT NULL PRIMARY KEY CLUSTERED   
+  , [Name] nvarchar(100) NOT NULL  
+  , [Position] varchar(100) NOT NULL   
+  , [Department] varchar(100) NOT NULL  
+  , [Address] nvarchar(1024) NOT NULL  
+  , [AnnualSalary] decimal (10,2) NOT NULL  
+  , [ValidFrom] datetime2 (2) GENERATED ALWAYS AS ROW START  
+  , [ValidTo] datetime2 (2) GENERATED ALWAYS AS ROW END  
+  , PERIOD FOR SYSTEM_TIME (ValidFrom, ValidTo)  
+ )    
+ WITH (SYSTEM_VERSIONING = ON (HISTORY_TABLE = dbo.EmployeeHistory));
\ No newline at end of file