RowExpressionTreeTranslator.java
/*
* Licensed 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 com.facebook.presto.expressions.translator;
import com.facebook.presto.spi.relation.CallExpression;
import com.facebook.presto.spi.relation.ConstantExpression;
import com.facebook.presto.spi.relation.InputReferenceExpression;
import com.facebook.presto.spi.relation.LambdaDefinitionExpression;
import com.facebook.presto.spi.relation.RowExpression;
import com.facebook.presto.spi.relation.RowExpressionVisitor;
import com.facebook.presto.spi.relation.SpecialFormExpression;
import com.facebook.presto.spi.relation.VariableReferenceExpression;
import static java.util.Objects.requireNonNull;
public class RowExpressionTreeTranslator<T, C>
{
private final RowExpressionTranslator<T, C> rowExpressionTranslator;
private final RowExpressionVisitor<TranslatedExpression<T>, C> visitor;
private RowExpressionTreeTranslator(RowExpressionTranslator<T, C> rowExpressionTranslator)
{
this.rowExpressionTranslator = requireNonNull(rowExpressionTranslator, "rowExpressionTranslator is null");
this.visitor = new TranslatingVisitor();
}
public TranslatedExpression<T> rewrite(RowExpression node, C context)
{
return node.accept(this.visitor, context);
}
public static <T, C> TranslatedExpression<T> translateWith(
RowExpression expression,
RowExpressionTranslator<T, C> translator,
C context)
{
return expression.accept(new RowExpressionTreeTranslator<>(translator).visitor, context);
}
private class TranslatingVisitor
implements RowExpressionVisitor<TranslatedExpression<T>, C>
{
@Override
public TranslatedExpression<T> visitCall(CallExpression call, C context)
{
return rowExpressionTranslator.translateCall(call, context, RowExpressionTreeTranslator.this);
}
@Override
public TranslatedExpression<T> visitInputReference(InputReferenceExpression reference, C context)
{
// InputReferenceExpression should only be used by Presto engine rather than connectors
throw new UnsupportedOperationException("Cannot translate RowExpression that contains inputReferenceExpression");
}
@Override
public TranslatedExpression<T> visitConstant(ConstantExpression literal, C context)
{
return rowExpressionTranslator.translateConstant(literal, context, RowExpressionTreeTranslator.this);
}
@Override
public TranslatedExpression<T> visitLambda(LambdaDefinitionExpression lambda, C context)
{
return rowExpressionTranslator.translateLambda(lambda, context, RowExpressionTreeTranslator.this);
}
@Override
public TranslatedExpression<T> visitVariableReference(VariableReferenceExpression reference, C context)
{
return rowExpressionTranslator.translateVariable(reference, context, RowExpressionTreeTranslator.this);
}
@Override
public TranslatedExpression<T> visitSpecialForm(SpecialFormExpression specialForm, C context)
{
return rowExpressionTranslator.translateSpecialForm(specialForm, context, RowExpressionTreeTranslator.this);
}
}
}