DistinctPredicatesRule.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.And;
import org.apache.doris.nereids.trees.expressions.CompoundPredicate;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.util.ExpressionUtils;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;

import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

/**
 * Remove redundant expr for 'CompoundPredicate'.
 * for example:
 * transform (a = 1) and (b > 2) and (a = 1)  to (a = 1) and (b > 2)
 * transform (a = 1) or (a = 1) to (a = 1)
 */
public class DistinctPredicatesRule implements ExpressionPatternRuleFactory {
    public static final DistinctPredicatesRule INSTANCE = new DistinctPredicatesRule();

    @Override
    public List<ExpressionPatternMatcher<? extends Expression>> buildRules() {
        return ImmutableList.of(
                matchesTopType(CompoundPredicate.class).then(DistinctPredicatesRule::distinct)
                        .toRule(ExpressionRuleType.DISTINCT_PREDICATES)
        );
    }

    private static Expression distinct(CompoundPredicate expr) {
        List<Expression> extractExpressions = ExpressionUtils.extract(expr);
        Set<Expression> distinctExpressions = new LinkedHashSet<>(extractExpressions);
        if (distinctExpressions.size() != extractExpressions.size()) {
            return ExpressionUtils.compound(expr instanceof And, Lists.newArrayList(distinctExpressions));
        }
        return expr;
    }
}