Configuration and State

We need to fill in implementations for each of the required functions, but we won't need all of these to work just yet.

First, you'll see that we define three types: RawConfiguration, Configuration, and State.

Let's define those now above the connector and start function:

Copy
type RawConfiguration = {
  tables: TableConfiguration[];
};

type TableConfiguration = {
  tableName: string;
  columns: { [k: string]: Column };
};

type Column = {};

type Configuration = RawConfiguration;

type State = {
  db: Database;
};

RawConfiguration is the type of configuration that the user will see. By convention, this configuration should be enough to reproducibly determine the connector's schema, so for our SQLite connector, we configure the connector with an array of tables that we want to expose. Each of these table types in TableConfiguration is defined by its name and a list of columns.

Columns don't have any specific configuration yet, but we leave an empty object type here because we might want to capture things like column types later on.

The Configuration type is supposed to be a validated version of the raw configuration, but for our purposes, we'll reuse the same type.

State

The State type is for things like connection pools, handles, or any non-serializable state that gets allocated on startup, and which lives for the lifetime of the connector. For our connector, we need to keep a handle to our SQLite database.

Cool, so now that we've got our types defined, we can fill in the function definitions which the connector requires in order to interact with our SQLite database and Hasura DDN. Let's do that in the next step.