# Part VII. Databases providers for developers

For each database engine, Libgda requires an object which maps Libgda's API to the native API offered by that database engine. That object, a database provider needs to inherit GdaServerProvider and implement its virtual methods.

Database provider objects are generally instantiated once by the Libgda framework and can be used several times to open and work on connections to several databases of the same type.

Since Libgda itself is developed in the C language, and that most providers are also implemented in that language, the Libgda library itself contains a set of helper classes and functions to guide you in the addition of a new provider to the GDA framework. Two reference implementations are provided in the `providers/skel-implementation` directory of Libgda's sources:

- in `providers/skel-implementation/capi`: a skeleton implementation from scratch for a database accessed through a C API, where all the methods to implement are partially coded

- in `providers/skel-implementation/models`: a skeleton implementation to write a provider for sources which are not databases (which do not implement any SQL) such as the Berkeley DB provider (a BDB database is a key/value collection) or the MDB (MS Access files) provider. This kind of provider "export" tables which are in fact data models.

The helper objects and functions to write database providers are documented in the Providers' support API section.

## Getting started

Libgda's sources contain templates to get started in creating a new database provider. The following templates are available:

- the template in the `providers/skel-implementation/capi` directory which can be used when writing a provider using the database's C or C++ API (for example the PostgreSQL or MySQL providers)

- the template in the `providers/skel-implementation/models` directory which can be used when writing a provider for a system which is not a relational database (or does offer a very limited API, such as for the MS Access or Berkeley DB systems).

In any case, for example to create a DummyDb provider, follow these steps:

- copy one of the template's directory into a new directory named `dummydb`

- From inside that new directory, run the `providers/prepare_provider_sources.sh` script with the name of the provider as sole argument ("dummydb" here), which replaces all the class and object names with the name of the provider and renames the files correctly. These new sources should be compilable without any modification.

- Edit the `Makefile.am` to add provider specific compilation and link flags

- Integrate the provider's new code into a compilation unit: either Libgda's sources in the `providers`directory or in your own application (this step usually involves modifying the `configure.ac` or `configure.in` files).

- Implement the missing parts (it is usually a good idea to look how other provider's implementations are done to get ideas).