/*
* 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.sql.planner;
import com.facebook.presto.sql.tree.Expression;
import com.facebook.presto.sql.tree.ExpressionRewriter;
import com.facebook.presto.sql.tree.ExpressionTreeRewriter;
import com.facebook.presto.sql.tree.FieldReference;
import com.facebook.presto.sql.tree.LambdaExpression;
import com.facebook.presto.sql.tree.SymbolReference;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import java.util.Map;
import static java.util.Objects.requireNonNull;
public class SymbolToInputRewriter
{
private final Map<Symbol, Integer> symbolToChannelMapping;
public SymbolToInputRewriter(Map<Symbol, Integer> symbolToChannelMapping)
{
requireNonNull(symbolToChannelMapping, "symbolToChannelMapping is null");
this.symbolToChannelMapping = ImmutableMap.copyOf(symbolToChannelMapping);
}
public Expression rewrite(Expression expression)
{
return ExpressionTreeRewriter.rewriteWith(new ExpressionRewriter<Context>() {
@Override
public Expression rewriteSymbolReference(SymbolReference node, Context context, ExpressionTreeRewriter<Context> treeRewriter)
{
Integer channel = symbolToChannelMapping.get(Symbol.from(node));
if (channel == null) {
Preconditions.checkArgument(context.isInLambda(), "Cannot resolve symbol %s", node.getName());
return node;
}
return new FieldReference(channel);
}
@Override
public Expression rewriteLambdaExpression(LambdaExpression node, Context context, ExpressionTreeRewriter<Context> treeRewriter)
{
return treeRewriter.defaultRewrite(node, new Context(true));
}
}, expression, new Context(false));
}
private static class Context
{
private final boolean inLambda;
public Context(boolean inLambda)
{
this.inLambda = inLambda;
}
public boolean isInLambda()
{
return inLambda;
}
}
}