org.apache.calcite.schema

Interface Member

public interface Member

A named expression in a schema.

Examples of members

Several kinds of members crop up in real life. They all implement the Member interface, but tend to be treated differently by the back-end system if not by Calcite.

A member that has zero arguments and a type that is a collection of records is referred to as a relation. In schemas backed by a relational database, tables and views will appear as relations.

A member that has one or more arguments and a type that is a collection of records is referred to as a parameterized relation. Some relational databases support these; for example, Oracle calls them "table functions".

Members may be also more typical of programming-language functions: they take zero or more arguments, and return a result of arbitrary type.

From the above definitions, you can see that a member is a special kind of function. This makes sense, because even though it has no arguments, it is "evaluated" each time it is used in a query.

Method Summary

Methods

Modifier and Type	Method and Description
Queryable	evaluate(Object schemaInstance, List<Object> arguments) Evaluates this member to yield a result.
String	getName() The name of this function.
List<FunctionParameter>	getParameters() Returns the parameters of this member.
RelDataType	getType() Returns the type of this function's result.

Method Detail

getName

String getName()

The name of this function.

getParameters

List<FunctionParameter> getParameters()

Returns the parameters of this member.

Returns:

Parameters; never null

getType

RelDataType getType()

Returns the type of this function's result.

Returns:

Type of result; never null

evaluate

Queryable evaluate(Object schemaInstance,
                 List<Object> arguments)

Evaluates this member to yield a result. The result is a Queryable.

Parameters:

schemaInstance - Object that is an instance of the containing Schema

arguments - List of arguments to the call; must match parameters in number and type

Returns:

An instance of this schema object, as a Queryable