io.prestosql.sql.planner.iterative.rule.ImplementExceptAsUnion 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.prestosql.sql.planner.iterative.rule;
import com.google.common.collect.ImmutableList;
import io.prestosql.matching.Captures;
import io.prestosql.matching.Pattern;
import io.prestosql.metadata.Metadata;
import io.prestosql.sql.planner.iterative.Rule;
import io.prestosql.sql.planner.plan.Assignments;
import io.prestosql.sql.planner.plan.ExceptNode;
import io.prestosql.sql.planner.plan.FilterNode;
import io.prestosql.sql.planner.plan.ProjectNode;
import io.prestosql.sql.tree.Expression;
import io.prestosql.sql.tree.NotExpression;
import java.util.List;
import static com.google.common.collect.Iterables.getFirst;
import static io.prestosql.sql.ExpressionUtils.and;
import static io.prestosql.sql.planner.plan.Patterns.except;
import static java.util.Objects.requireNonNull;
/**
* Converts EXCEPT queries into UNION ALL..GROUP BY...WHERE
* E.g.:
*
* SELECT a FROM foo
* EXCEPT
* SELECT x FROM bar
*
* =>
*
* SELECT a
* FROM
* (
* SELECT a,
* COUNT(foo_marker) AS foo_count,
* COUNT(bar_marker) AS bar_count
* FROM
* (
* SELECT a, true as foo_marker, null as bar_marker
* FROM foo
* UNION ALL
* SELECT x, null as foo_marker, true as bar_marker
* FROM bar
* ) T1
* GROUP BY a
* ) T2
* WHERE foo_count >= 1 AND bar_count = 0;
*
*/
public class ImplementExceptAsUnion
implements Rule
{
private static final Pattern PATTERN = except();
private final Metadata metadata;
public ImplementExceptAsUnion(Metadata metadata)
{
this.metadata = requireNonNull(metadata, "metadata is null");
}
@Override
public Pattern getPattern()
{
return PATTERN;
}
@Override
public Result apply(ExceptNode node, Captures captures, Context context)
{
SetOperationNodeTranslator translator = new SetOperationNodeTranslator(metadata, context.getSymbolAllocator(), context.getIdAllocator());
SetOperationNodeTranslator.TranslationResult result = translator.makeSetContainmentPlan(node);
ImmutableList.Builder predicatesBuilder = ImmutableList.builder();
List presentExpression = result.getPresentExpressions();
predicatesBuilder.add(getFirst(presentExpression, null));
for (int i = 1; i < presentExpression.size(); i++) {
predicatesBuilder.add(new NotExpression(presentExpression.get(i)));
}
return Result.ofPlanNode(
new ProjectNode(
context.getIdAllocator().getNextId(),
new FilterNode(context.getIdAllocator().getNextId(), result.getPlanNode(), and(predicatesBuilder.build())),
Assignments.identity(node.getOutputSymbols())));
}
}