LakshSingla commented on code in PR #14981: URL: https://github.com/apache/druid/pull/14981#discussion_r1342364975
########## sql/src/main/java/org/apache/druid/sql/calcite/rule/DruidFreeUnionDataSourceRule.java: ########## @@ -0,0 +1,150 @@ +/* + * 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.druid.sql.calcite.rule; + +import org.apache.calcite.plan.RelOptRule; +import org.apache.calcite.plan.RelOptRuleCall; +import org.apache.calcite.rel.RelNode; +import org.apache.calcite.rel.core.Union; +import org.apache.druid.sql.calcite.planner.PlannerContext; +import org.apache.druid.sql.calcite.rel.DruidFreeUnionDataSourceRel; +import org.apache.druid.sql.calcite.rel.DruidRel; + +import javax.annotation.Nullable; +import java.util.Collections; +import java.util.List; +import java.util.Optional; + +/** + * Creates a {@link DruidFreeUnionDataSourceRel} from various {@link DruidRel} inputs that represents ad hoc scans + * + */ +public class DruidFreeUnionDataSourceRule extends RelOptRule +{ + private final PlannerContext plannerContext; + + public DruidFreeUnionDataSourceRule(final PlannerContext plannerContext) + { + super( + operand( + Union.class, + operand(DruidRel.class, none()), + operand(DruidRel.class, none()) + ) + ); + this.plannerContext = plannerContext; + } + + @Override + public boolean matches(RelOptRuleCall call) + { + final Union unionRel = call.rel(0); + final DruidRel<?> firstDruidRel = call.rel(1); + final DruidRel<?> secondDruidRel = call.rel(2); + + return isCompatible(unionRel, firstDruidRel, secondDruidRel, plannerContext); + } + + @Override + public void onMatch(final RelOptRuleCall call) + { + final Union unionRel = call.rel(0); + final DruidRel<?> firstDruidRel = call.rel(1); + final DruidRel<?> secondDruidRel = call.rel(2); + + if (firstDruidRel instanceof DruidFreeUnionDataSourceRel) { + // Unwrap and flatten the inputs to the Union. + final RelNode newUnionRel = call.builder() + .pushAll(firstDruidRel.getInputs()) + .push(secondDruidRel) + .union(true, firstDruidRel.getInputs().size() + 1) + .build(); + + call.transformTo( + DruidFreeUnionDataSourceRel.create( + (Union) newUnionRel, + getColumnNames(firstDruidRel, plannerContext).get(), + firstDruidRel.getPlannerContext() + ) + ); + } else { + call.transformTo( + DruidFreeUnionDataSourceRel.create( + unionRel, + getColumnNames(firstDruidRel, plannerContext).get(), + firstDruidRel.getPlannerContext() + ) + ); + } + } + + // Can only do UNION ALL of inputs that have compatible schemas (or schema mappings) and right side + // is a simple table scan + public static boolean isCompatible( + final Union unionRel, + final DruidRel<?> first, + final DruidRel<?> second, + @Nullable PlannerContext plannerContext + ) + { + if (second instanceof DruidFreeUnionDataSourceRel) { + return false; + } + + if (!unionRel.all && null != plannerContext) { + plannerContext.setPlanningError("SQL requires 'UNION' but only 'UNION ALL' is supported."); + } + return unionRel.all && isUnionCompatible(first, second, plannerContext); + } + + /** + * For the current implementation the union is compatible iff the column's data types column and names are same + */ + private static boolean isUnionCompatible( + final DruidRel<?> first, + final DruidRel<?> second, + @Nullable PlannerContext plannerContext + ) + { + final Optional<List<String>> firstColumnNames = getColumnNames(first, plannerContext); + final Optional<List<String>> secondColumnNames = getColumnNames(second, plannerContext); + if (!firstColumnNames.isPresent() || !secondColumnNames.isPresent()) { + // No need to set the planning error here + return false; + } + if (!firstColumnNames.equals(secondColumnNames)) { Review Comment: If the union is nested inside a subquery, it would be difficult for the upper callers to reference it once it has changed into the form EXPR$0, due to implicit casting. Therefore if we can identify that it has been cast implicitly, then we should remap it back to the original column name, else I am debating that we should include name and the type check, -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
