io.trino.sql.ir.optimizer.rule.EvaluateCase Maven / Gradle / Ivy
/*
* 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 io.trino.sql.ir.optimizer.rule;
import io.trino.Session;
import io.trino.sql.ir.Case;
import io.trino.sql.ir.Constant;
import io.trino.sql.ir.Expression;
import io.trino.sql.ir.WhenClause;
import io.trino.sql.ir.optimizer.IrOptimizerRule;
import io.trino.sql.planner.Symbol;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import static io.trino.sql.ir.Booleans.TRUE;
/**
* Evaluates a constant Case expression: {@code Case(When(TRUE, r), When(...), When(...)} -> {@code r}
*/
public class EvaluateCase
implements IrOptimizerRule
{
@Override
public Optional apply(Expression expression, Session session, Map bindings)
{
if (!(expression instanceof Case(List whenClauses, Expression defaultValue))) {
return Optional.empty();
}
for (WhenClause whenClause : whenClauses) {
Expression operand = whenClause.getOperand();
if (operand.equals(TRUE)) {
return Optional.of(whenClause.getResult());
}
else if (!(operand instanceof Constant)) {
return Optional.empty();
}
}
return Optional.of(defaultValue);
}
}