Delphi Prism

by John 10/29/2008 2:22:00 AM

I'm looking forward to what the future holds for object pascal on the .Net platform.

I've been studying the various press releases here and here and I can't wait to start using it. 

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Delphi

Schema generation using database migrations - NorthWind for Blackfish

by John 7/20/2008 10:20:00 PM

Recently I've been maintaining my database schema changes using DBXExpress, more about the process I follow can be found here

I'm currently moving an application from MS Sql Server to Blackfish and unfortunately all I really have is a bunch of MS Sql specific scripts. I wished I had a set of migrations that I could use as the basis for my Blackfish database, so I decided to dive into DBExpress again and I have extended the MSBuild tasks I created to generate Delphi code that I could use as a starting point.

In the screenshot below can be seen the tables of the SQL Server version of the "NorthWind" database and on the right a Blackfish version.

An updated version of the original code can be found here.

As with the previous version having downloaded the code from codecentral, the first thing that needs to be done is to open up the "MigrationProjectGroup.groupproj" projectgroup

in the root directory. In the new version I have added a new package called Moshine.SchemaGenerationTest. In the download it contains a schema generation which are .pas files used to create the Northwind tables using dbxexpress. If you wish to re-generate, you can remove the .pas files from this package so that it would look like the screenshot below.

 

 

The important part of the project are the 2 msbuild target files and an app.config

The app.config contains two connection strings, one for MSSQL Server and the other for the Blackfish database that will be created. You are quite likely going to have to modify those so that they match your environment.

Generation.targets contains the specification for the schema generation and a copy can be seen below

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">

    <UsingTask TaskName="Moshine.Migration.MSBuild.TMigrationSchemaGenerationTask"
            AssemblyFile="..\Moshine.MSBuildMigration\bin\Moshine.MSBuildMigration.dll" />

    <PropertyGroup>
        <MigrationAssembly>bin\Moshine.SchemaGenerationTest.dll</MigrationAssembly>
        <ConnectionName>NorthwindConnection</ConnectionName>
        <DestinationDirectory>d:\develop\moshine\Migration\Moshine.SchemaGenerationTest</DestinationDirectory>
        <Namespace>Moshine.SchemaGenerationTest</Namespace>
        <UpperCaseTableNames>true</UpperCaseTableNames>
    </PropertyGroup>

    <Target Name="SchemaGeneration">
        <TMigrationSchemaGenerationTask  UpperCaseTableNames="$(UpperCaseTableNames)" Namespace="$(Namespace)" DestinationDirectory="$(DestinationDirectory)" MigrationAssembly="$(MigrationAssembly)" ConnectionName="$(ConnectionName)" />
    </Target>

</Project>

DestinationDirectory contains the target directorty for the schema generation, your most likely going to have to change this.

Once the projectgroup has been built you should be able to move to a RAD Studio command prompt from which you can generate the schema.

The commandline from the Moshine.SchemaGenerateTest directory is MSBUILD generation.targets -t:SchemaGeneration 

You can also execute the MSBuild task from the IDE by right clicking on the  Generation.targets file in the project manager and performing a  targets/schemageneration

The actual code that performs the code generation is in the Moshine.Migration.Framework project as Moshine.Migration.Framework.MigrationGenerator.pas. I have tested against the MSSQL Server database Northwind that is used in quite a few Microsoft demos and against the database I'm migrating. In theory it should work against other MS SQL Server databases and any other database supported by DBXExpress. I haven't supported every datatype so you might get an error like this.

In which case you will have to modify the generator code, which shouldn't be too difficult :)

Assuming the schema generation went ok you should have .pas files in the  generation directory. Its 1 file per database table.

The screenshot below shows the files for Northwind

You can then add the files to the SchemaGenerationTest project and rebuild. The resulting assembly is going to be used to build the Blackfish database.

The generated code looks like the sample below

 

procedure TCreateTableShippersMigration.Up;
var
tableMetaData: TDBXMetaDataTable;
newTDBXWideVarCharColumn: TDBXWideVarCharColumn;
newTDBXInt32Column: TDBXInt32Column;
begin
tableMetaData := TDBXMetaDataTable.Create();
tableMetaData.TableName:='SHIPPERS';
newTDBXInt32Column:= TDBXInt32Column.Create('ShipperID');
newTDBXInt32Column.AutoIncrement:=true;
if(not self.Provider.CheckColumnSupported(newTDBXInt32Column))then
begin
newTDBXInt32Column.AutoIncrement:=false;
end;
newTDBXInt32Column.Nullable:=false;
tableMetaData.AddColumn(newTDBXInt32Column);
newTDBXWideVarCharColumn:= TDBXWideVarCharColumn.Create('CompanyName',40);
newTDBXWideVarCharColumn.Nullable:=false;
tableMetaData.AddColumn(newTDBXWideVarCharColumn);
newTDBXWideVarCharColumn:= TDBXWideVarCharColumn.Create('Phone',24);
tableMetaData.AddColumn(newTDBXWideVarCharColumn);
provider.CreateTable(tableMetaData);
self.AddPrimaryKey('ShipperID','SHIPPERS');
end;

This is DBXExpress Delphi code to create the SHIPPERS database table. Each class corresponds to 1 step in a migration. 

Having successfully built the assembly the second targets file Migration.Targets in the SchemaGenerationTest project can be used. You can right click on the

Migration.Targets file in the project manager and perform Targets/migration. 

From a CodeGear command prompt this would be MSBUILD migration.targets-t:migration. Assuming that the migration was performed you should have a Blackfish database

with the tables created. As I mentioned before you be able to perform a code generation and migration against any database that DBXExpress supports.

The generated code only creates the tables from the source schema but it should be a good starting point from which you can add your own code to further extend the migration and the database schema.

Feedback is welcome and the source can be found in CodeCentral here 

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Tags:

Database | dbx4 | msbuild | migration | Blackfish | Delphi

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Name of author John Moshakis
I'm a software developer living in Toronto..

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