Types#
Примечание
Ниже приведена оригинальная документация Trino. Скоро мы ее переведем на русский язык и дополним полезными примерами.
The Type
interface in Trino is used to implement a type in the SQL language.
Trino 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)
.