ProjectToGlobalAggregate.java

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package org.apache.doris.nereids.rules.analysis;

import org.apache.doris.nereids.rules.Rule;
import org.apache.doris.nereids.rules.RuleType;
import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitors;
import org.apache.doris.nereids.trees.plans.logical.LogicalAggregate;

import com.google.common.collect.ImmutableList;

/**
 * ProjectToGlobalAggregate.
 * <p>
 * example sql:
 * <pre>
 * select sum(value)
 * from tbl
 * </pre>
 *
 * origin plan:                                                 transformed plan:
 * <p>
 * LogicalProject(projects=[sum(value)])                        LogicalAggregate(groupBy=[], output=[sum(value)])
 *            |                                      =>                              |
 *  LogicalOlapScan(table=tbl)                                                  LogicalOlapScan(table=tbl)
 */
public class ProjectToGlobalAggregate extends OneAnalysisRuleFactory {
    @Override
    public Rule build() {
        return RuleType.PROJECT_TO_GLOBAL_AGGREGATE.build(
           logicalProject().then(project -> {
               boolean needGlobalAggregate = project.getProjects()
                       .stream()
                       .anyMatch(p -> p.accept(ExpressionVisitors.CONTAINS_AGGREGATE_CHECKER, null));

               if (needGlobalAggregate) {
                   return new LogicalAggregate<>(ImmutableList.of(), project.getProjects(), project.child());
               } else {
                   return project;
               }
           })
        );
    }
}