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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to you under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.calcite.schema;
import org.apache.calcite.linq4j.Queryable;
import org.apache.calcite.rel.type.RelDataType;
import java.util.List;
/**
* A named expression in a schema.
*
* Examples of members
*
* Several kinds of members crop up in real life. They all implement the
* {@code 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.
*/
public interface Member {
/**
* The name of this function.
*/
String getName();
/**
* Returns the parameters of this member.
*
* @return Parameters; never null
*/
List getParameters();
/**
* Returns the type of this function's result.
*
* @return Type of result; never null
*/
RelDataType getType();
/**
* Evaluates this member to yield a result. The result is a
* {@link org.apache.calcite.linq4j.Queryable}.
*
* @param schemaInstance Object that is an instance of the containing
* {@link Schema}
* @param arguments List of arguments to the call; must match
* {@link #getParameters() parameters} in number and type
*
* @return An instance of this schema object, as a Queryable
*/
Queryable evaluate(
Object schemaInstance,
List