From 0e6746644e075d888ae1856e712b389df9bafd7e Mon Sep 17 00:00:00 2001
From: Tim Thompson <github@wokket.com>
Date: Mon, 6 Jun 2022 00:52:31 +1000
Subject: [PATCH] =?UTF-8?q?fix=20#167:=20Ensure=20that=20a=20sql=20server?=
 =?UTF-8?q?=20database=20name=20that=20differs=20only=20by=E2=80=A6=20(#19?=
 =?UTF-8?q?5)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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---
 grate.unittests/Generic/GenericDatabase.cs | 18 ++++++++++++++
 grate/Migration/SqlServerDatabase.cs       | 28 ++++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/grate.unittests/Generic/GenericDatabase.cs b/grate.unittests/Generic/GenericDatabase.cs
index 95cc7a70..1ab33690 100644
--- a/grate.unittests/Generic/GenericDatabase.cs
+++ b/grate.unittests/Generic/GenericDatabase.cs
@@ -87,6 +87,24 @@ public async Task Does_not_need_admin_connection_if_database_already_exists()
         Assert.DoesNotThrowAsync(() => migrator.Migrate());
     }
 
+    [Test]
+    public async Task Does_not_needlessly_apply_case_sensitive_database_name_checks_Issue_167()
+    {
+        // There's a bug where if the database name specified by the user differs from the actual database only by case then
+        // Grate currently attempts to create the database again, only for it to fail on the DBMS (Sql Server bug only).
+
+        var db = "CASEDATABASE";
+        await CreateDatabase(db);
+
+        // Check that the database has been created
+        IEnumerable<string> databasesBeforeMigration = await GetDatabases();
+        databasesBeforeMigration.Should().Contain(db);
+
+        await using var migrator = GetMigrator(GetConfiguration(db.ToLower(), true)); // ToLower is important here, this reproduces the bug in #167
+        // There should be no errors running the migration
+        Assert.DoesNotThrowAsync(() => migrator.Migrate());
+    }
+
     protected virtual async Task CreateDatabase(string db)
     {
         using (new TransactionScope(TransactionScopeOption.Suppress, TransactionScopeAsyncFlowOption.Enabled))
diff --git a/grate/Migration/SqlServerDatabase.cs b/grate/Migration/SqlServerDatabase.cs
index b70c7c1e..44a534e5 100644
--- a/grate/Migration/SqlServerDatabase.cs
+++ b/grate/Migration/SqlServerDatabase.cs
@@ -1,12 +1,16 @@
 using System;
 using System.Data.Common;
+using System.Linq;
 using System.Threading.Tasks;
 using System.Transactions;
+using Dapper;
 using grate.Configuration;
 using grate.Infrastructure;
 using Microsoft.Data.SqlClient;
 using Microsoft.Extensions.Logging;
 
+using static System.Data.CommandType;
+
 namespace grate.Migration;
 
 public class SqlServerDatabase : AnsiSqlDatabase
@@ -68,4 +72,28 @@ WITH NOUNLOAD
 
         Logger.LogInformation("Database {DbName} successfully restored from path {Path}.", DatabaseName, backupPath);
     }
+
+    public override async Task<bool> DatabaseExists()
+    {
+        // For Bug #167.  Sql Server is causing issues when the database name passed in differs only in case from one already existing on the server.
+        // There's currently no point adding to ISyntax for this as all the other DBMS's would just be a NOP.
+
+        // This should also mean that a SQL server running a Case Sensitive collation _also_ works as expected
+        var sql = $"select name from sys.databases where [name] = '{DatabaseName}'";
+        try
+        {
+            await OpenConnection();
+            var results = await Connection.QueryAsync<string>(sql, commandType: Text);
+            return results.Any();
+        }
+        catch (DbException ex)
+        {
+            Logger.LogDebug(ex, "An unexpected error occurred performing the CheckDatabaseExists check: {ErrorMessage}", ex.Message);
+            return false; // base method also returns false on any DbException
+        }
+        finally
+        {
+            await CloseConnection();
+        }
+    }
 }