org.apache.hadoop.hive.ql.exec.ExprNodeEvaluator Maven / Gradle / Ivy
/**
* 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.hadoop.hive.ql.exec;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.plan.ExprNodeDesc;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
/**
* ExprNodeEvaluator.
*
*/
public abstract class ExprNodeEvaluator {
protected final T expr;
protected ObjectInspector outputOI;
public ExprNodeEvaluator(T expr) {
this.expr = expr;
}
/**
* Return child evaluators if exist
*/
public T getExpr() {
return expr;
}
/**
* Initialize should be called once and only once. Return the ObjectInspector
* for the return value, given the rowInspector.
*/
public abstract ObjectInspector initialize(ObjectInspector rowInspector) throws HiveException;
/**
* Return initialized ObjectInspector. If it's not initialized, throws runtime exception
*/
public ObjectInspector getOutputOI() {
if (outputOI == null) {
throw new IllegalStateException("Evaluator is not initialized");
}
return outputOI;
}
private transient int version = -1;
private transient Object evaluation;
public Object evaluate(Object row) throws HiveException {
return evaluate(row, -1);
}
/**
* Evaluate the expression given the row. This method should use the
* rowInspector passed in from initialize to inspect the row object. The
* return value will be inspected by the return value of initialize.
* If this evaluator is referenced by others, store it for them
*/
protected Object evaluate(Object row, int version) throws HiveException {
if (version < 0 || version != this.version) {
this.version = version;
return evaluation = _evaluate(row, version);
}
return evaluation;
}
/**
* Evaluate value
*/
protected abstract Object _evaluate(Object row, int version) throws HiveException;
/**
* Return whether this node (and all children nodes) are deterministic.
*/
public boolean isDeterministic() {
return true;
}
/**
* Return whether this node (or any children nodes) are stateful.
*/
public boolean isStateful() {
return false;
}
/**
* Return child evaluators if exist
*/
public ExprNodeEvaluator[] getChildren() {
return null;
}
@Override
public String toString() {
return "ExprNodeEvaluator[" + expr + "]";
}
}