Adding 'GO' statements to Entity Framework

问题:

So I have an application with a ton of migrations made by Entity framework. We want to get a script for all the migrations at once and using the -Script tag does work fine.

However...it does not add GO statements in the SQL giving us problems like Alter view should be the first statement in a batch file...

I have been searching around and manually adding Sql("GO"); help with this problem but only for the entire script. When I use the package console manager again it returns an exception.

System.Data.SqlClient.SqlException (0x80131904): Could not find stored procedure 'GO'.

Is there a way to add these GO tags only when using the -Script tag? If not, what is a good approach for this?

Note: we have also tried having multiple files but since we have so many migrations, this is near impossible to maintain every time.

回答1:

In order to change the SQL Generated by entity framework migrations you can create a new SqlServerMigrationSqlGenerator

We have done this to add a GO statement before and after the migration history:

public  class MigrationScriptBuilder: SqlServerMigrationSqlGenerator
{
    protected override void Generate(System.Data.Entity.Migrations.Model.InsertHistoryOperation insertHistoryOperation)
    {
        Statement("GO");

        base.Generate(insertHistoryOperation);

        Statement("GO");

    }
}

then add in the Configuration constructor (in the Migrations folder of the project where you DbContext is) so that it uses this new sql generator:

[...]
internal sealed class Configuration : DbMigrationsConfiguration<PMA.Dal.PmaContext>
{
    public Configuration()
    {
        SetSqlGenerator("System.Data.SqlClient", new MigrationScriptBuilder());
        AutomaticMigrationsEnabled = false;
    }
[...]

So now when you generate a script using the -Script tag, you can see that the insert into [__MigrationHistory] is surrounded by GO

Alternatively in your implementation of SqlServerMigrationSqlGenerator you can override any part of the script generation, the InsertHistoryOperation was suitable for us.

回答2:

If you are trying to alter your view using Sql('Alter View dbo.Foos As etc'), then you can avoid the should be the first statement in a batch file error without adding GO statements by putting the sql inside an EXEC command:

Sql(EXEC('Alter View dbo.Foos As etc'))

回答3:

Turn out the concept exist deep in the SqlServerMigrationSqlGenerator as an optional argument for Statement(sql, batchTerminator). Here is something based on Skyp idea. It works both in -script mode or not. The GOs are for different operations than for Skyp only because our needs are a little different. You then need to register this class in the Configuration as per Skyp instructions.

    public class MigrationScriptBuilder : SqlServerMigrationSqlGenerator
    {
        private string Marker = Guid.NewGuid().ToString(); //To cheat on the check null or empty of the base generator

        protected override void Generate(AlterProcedureOperation alterProcedureOperation)
        {
            SqlGo();
            base.Generate(alterProcedureOperation);
            SqlGo();
        }
        protected override void Generate(CreateProcedureOperation createProcedureOperation)
        {
            SqlGo();
            base.Generate(createProcedureOperation);
            SqlGo();
        }
        protected override void Generate(SqlOperation sqlOperation)
        {
            SqlGo();
            base.Generate(sqlOperation);
        }

        private void SqlGo()
        {
            Statement(Marker, batchTerminator: "GO");
        }

        public override IEnumerable<MigrationStatement> Generate(IEnumerable<MigrationOperation> migrationOperations, string providerManifestToken)
        {
            var result = new List<MigrationStatement>();
            var statements = base.Generate(migrationOperations, providerManifestToken);

            bool pendingBatchTerminator = false;
            foreach (var item in statements)
            {
                if(item.Sql == Marker && item.BatchTerminator == "GO")
                {
                    pendingBatchTerminator = true;
                }
                else
                {
                    if(pendingBatchTerminator)
                    {
                        item.BatchTerminator = "GO";
                        pendingBatchTerminator = false;
                    }
                    result.Add(item);
                }
            }

            return result;
        }
    }

回答4:

Just replace the current statement with a .Replace("GO", "");