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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.expressions;
import org.apache.flink.annotation.Internal;
import org.apache.flink.table.api.TableException;
/**
* A visitor for all {@link ResolvedExpression}s.
*
* All expressions of this visitor are the output of the API and might be passed to a planner.
*/
@Internal
public abstract class ResolvedExpressionVisitor implements ExpressionVisitor {
public final R visit(Expression other) {
if (other instanceof TableReferenceExpression) {
return visit((TableReferenceExpression) other);
} else if (other instanceof LocalReferenceExpression) {
return visit((LocalReferenceExpression) other);
} else if (other instanceof ResolvedExpression) {
return visit((ResolvedExpression) other);
}
throw new TableException("Unexpected unresolved expression received: " + other);
}
public abstract R visit(TableReferenceExpression tableReference);
public abstract R visit(LocalReferenceExpression localReference);
/** For resolved expressions created by the planner. */
public abstract R visit(ResolvedExpression other);
}