
# Types

The `Type` interface in openLooKeng is used to implement a type in the SQL language. openLooKeng ships with a number of built-in types, like `VarcharType` and `BigintType`. The `ParametricType` interface is used to provide type
parameters for types, to allow types like `VARCHAR(10)` or `DECIMAL(22, 5)`. A `Plugin` can provide new `Type` objects by returning them from `getTypes()` and new `ParametricType` objects by returning them from `getParametricTypes()`.

Below is a high level overview of the `Type` interface, for more details see the JavaDocs for `Type`.

-   Native container type:

    All types define the `getJavaType()` method, frequently referred to as the \"native container type\". This is the Java type used to hold values during execution and to store them in a `Block`. For example,
    this is the type used in the Java code that implements functions that produce or consume this `Type`.
    
-   Native encoding:

    The interpretation of a value in its native container type form is defined by its `Type`. For some types, such as `BigintType`, it matches the Java interpretation of the native container type (64bit 2\'s complement). However, for other types such as `TimestampWithTimeZoneType`, which also uses `long` for its native container type, the value stored in the `long` is a 8byte binary value combining the timezone and the milliseconds since the unix  epoch. In particular, this means that you cannot compare two native values and expect a meaningful result, without knowing the native encoding.
    
-   Type signature:

    The signature of a type defines its identity, and also encodes some general information about the type, such as its type parameters (if it\'s parametric), and its literal parameters. The literal parameters are used in types like `VARCHAR(10)`.
