Migrating Data with TInstantPump

TInstantPump is a component that helps migrate data between InstantObjects databases. It can help in these circumstances:

• You have a database in a broker and want to move the data to a database of another broker (for example to Firebird or to SQL Server). InstantObjects eases the creation of the new database schema, while TInstantPump moves the data. In the general case you can migrate data using any combination of two connectors, provided the destination broker supports all the features you have used in the source database. For example, some brokers do not support external Parts and References, others do.
• You have decided to convert the Parts and References blobs from binary to XML format (see XML Blob Streaming). Create a new empty database, set the source connector to use binary blobs and the destination connector to use XML blobs, then run the pump.
• You need to change the data type or the size of the Id fields (see Id Data Type and Size).

TInstantPump currently cannot migrate data between different models (for example from the classic blob-based storage of the collections to external storage).

The demo Demos\Pump shows how to use the component.

Using TInstantPump

You hook the pump to a source connector (used to retrieve the objects from the source database) and to a destination connector (used to write the objects to the destination database).

Properties

Property	Description
SourceConnector: TInstantConnector	The source database. Set the properties of the connector (UseTransactions, BlobStreamFormat, IdDataType, IdSize...) to match those of the database.
DestConnector: TInstantConnector	The destination database. Set the properties of the connector the same way.
Options: set of TInstantPumpOption	Tweaks the pump process. poEmptyDestBeforePump empties each destination table before writing the objects to it. The default is [poEmptyDestBeforePump].

Methods

procedure Pump(Model: TInstantModel = nil);

Starts pumping. Passing an external model is not supported: pass nil, which means the component uses the global InstantModel. All the model units must therefore be part of the project: the pump works inside an InstantObjects project.

Events

Event	Description
BeforePump: TInstantSchemeEvent	Called before the pump, with the TInstantScheme built by the source connector: you can look at it (and possibly modify it; not tested).
AfterPump: TInstantSchemeEvent	The same, called after the pump process has finished.

Example

var
  Pump: TInstantPump;
begin
  Pump := TInstantPump.Create(nil);
  try
    Pump.SourceConnector := SQLConnector;
    Pump.DestConnector := XMLConnector;
    Pump.Options := [poEmptyDestBeforePump];
    Pump.Pump;
  finally
    Pump.Free;
  end;
end;

Pumping without the model units (not tested)

In principle the pump can be used without compiling the model units into the application. These are the steps:

1. create a package that holds the model units;
2. create a pump application with no model, compiled with run-time packages;
3. have the application load the model package dynamically with H := LoadPackage('MyModel.bpl'), and call UnloadPackage(H) when finished;
4. before calling Pump, load the model from an XML file or from an .mdr resource file: InstantModel.LoadFromFile('MyModel.xml') or InstantModel.LoadFromResFile('MyModel.mdr');
5. call Pump.

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Originally written by Nando Dessena, 2005.