CheckMultiDistinct.java

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

import org.apache.doris.nereids.exceptions.AnalysisException;
import org.apache.doris.nereids.rules.Rule;
import org.apache.doris.nereids.rules.RuleType;
import org.apache.doris.nereids.trees.expressions.functions.agg.AggregateFunction;
import org.apache.doris.nereids.trees.expressions.functions.agg.Avg;
import org.apache.doris.nereids.trees.expressions.functions.agg.Count;
import org.apache.doris.nereids.trees.expressions.functions.agg.GroupConcat;
import org.apache.doris.nereids.trees.expressions.functions.agg.Sum;
import org.apache.doris.nereids.trees.expressions.functions.agg.Sum0;
import org.apache.doris.nereids.trees.plans.Plan;
import org.apache.doris.nereids.trees.plans.logical.LogicalAggregate;

import com.google.common.collect.ImmutableSet;

/**
 * If there are multiple distinct aggregate functions that cannot
 * be transformed into multi_distinct, an error is reported.
 * The following functions can be transformed into multi_distinct:
 * - count -> MULTI_DISTINCT_COUNT
 * - sum -> MULTI_DISTINCT_SUM
 * - avg -> MULTI_DISTINCT_AVG
 * - group_concat -> MULTI_DISTINCT_GROUP_CONCAT
 */
public class CheckMultiDistinct extends OneRewriteRuleFactory {
    private final ImmutableSet<Class<? extends AggregateFunction>> supportedFunctions =
            ImmutableSet.of(Count.class, Sum.class, Avg.class, GroupConcat.class, Sum0.class);

    @Override
    public Rule build() {
        return logicalAggregate().then(agg -> checkDistinct(agg)).toRule(RuleType.CHECK_ANALYSIS);
    }

    private LogicalAggregate checkDistinct(LogicalAggregate<? extends Plan> aggregate) {
        if (aggregate.getDistinctArguments().size() > 1) {

            for (AggregateFunction func : aggregate.getAggregateFunctions()) {
                if (func.isDistinct() && !supportedFunctions.contains(func.getClass())) {
                    throw new AnalysisException(func.toString() + " can't support multi distinct.");
                }
            }
        }
        return aggregate;
    }
}