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LookupCallResolver.java
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LookupCallResolver.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.expressions;
import org.apache.flink.annotation.Internal;
import org.apache.flink.table.api.ValidationException;
import org.apache.flink.table.catalog.FunctionLookup;
import org.apache.flink.table.functions.FunctionDefinition;
import java.util.List;
import static org.apache.flink.table.expressions.ApiExpressionUtils.call;
/**
* Resolves calls with function names to calls with actual function definitions.
*/
@Internal
public class LookupCallResolver extends ApiExpressionDefaultVisitor<Expression> {
private final FunctionLookup functionLookup;
public LookupCallResolver(FunctionLookup functionLookup) {
this.functionLookup = functionLookup;
}
public Expression visit(LookupCallExpression lookupCall) {
final FunctionLookup.Result result = functionLookup.lookupFunction(lookupCall.getUnresolvedName())
.orElseThrow(() -> new ValidationException("Undefined function: " + lookupCall.getUnresolvedName()));
return createResolvedCall(result.getFunctionDefinition(), lookupCall.getChildren());
}
public Expression visit(CallExpression call) {
return createResolvedCall(call.getFunctionDefinition(), call.getChildren());
}
private Expression createResolvedCall(FunctionDefinition functionDefinition, List<Expression> unresolvedChildren) {
final Expression[] resolvedChildren = unresolvedChildren
.stream()
.map(child -> child.accept(this))
.toArray(Expression[]::new);
return call(functionDefinition, resolvedChildren);
}
@Override
protected Expression defaultMethod(Expression expression) {
return expression;
}
}