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FunctionDefinition.java
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FunctionDefinition.java
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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.flink.table.functions;
import org.apache.flink.annotation.PublicEvolving;
import java.util.Collections;
import java.util.Set;
/**
* Definition of a function. Instances of this class provide all details necessary to validate a function
* call and perform planning.
*
* <p>A pure function definition must not contain a runtime implementation. This can be provided by
* the planner at later stages.
*
* @see UserDefinedFunction
*/
@PublicEvolving
public interface FunctionDefinition {
/**
* Returns the kind of function this definition describes.
*/
FunctionKind getKind();
/**
* Returns the language of function this definition describes.
*/
default FunctionLanguage getLanguage() {
return FunctionLanguage.JVM;
}
/**
* Returns the set of requirements this definition demands.
*/
default Set<FunctionRequirement> getRequirements() {
return Collections.emptySet();
}
/**
* Returns information about the determinism of the function's results.
*
* <p>It returns <code>true</code> if and only if a call to this function is guaranteed to
* always return the same result given the same parameters. <code>true</code> is
* assumed by default. If the function is not pure functional like <code>random(), date(), now(), ...</code>
* this method must return <code>false</code>.
*/
default boolean isDeterministic() {
return true;
}
}