MedianConvert.java

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

import org.apache.doris.nereids.rules.expression.ExpressionPatternMatcher;
import org.apache.doris.nereids.rules.expression.ExpressionPatternRuleFactory;
import org.apache.doris.nereids.rules.expression.ExpressionRuleType;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.functions.agg.Median;
import org.apache.doris.nereids.trees.expressions.functions.agg.Percentile;
import org.apache.doris.nereids.trees.expressions.literal.DoubleLiteral;

import com.google.common.collect.ImmutableList;

import java.util.List;

/**
 * median(col) -> percentile(col, 0.5)
 */
public class MedianConvert implements ExpressionPatternRuleFactory {
    public static MedianConvert INSTANCE = new MedianConvert();

    @Override
    public List<ExpressionPatternMatcher<? extends Expression>> buildRules() {
        return ImmutableList.of(
                matchesType(Median.class).then(median ->
                    new Percentile(median.child(0), DoubleLiteral.of(0.5))
                ).toRule(ExpressionRuleType.MEDIAN_CONVERT)
        );
    }
}