Monotonic.java

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package org.apache.doris.nereids.trees.expressions.functions;

import org.apache.doris.nereids.rules.expression.ExpressionRewriteContext;
import org.apache.doris.nereids.rules.expression.rules.ColumnRange;
import org.apache.doris.nereids.trees.expressions.literal.Literal;

import java.util.Optional;

/** monotonicity of expressions */
public interface Monotonic extends RangeInferable {
    default boolean isMonotonic(Literal lower, Literal upper) {
        return true;
    }

    // true means that the function is an increasing function
    boolean isPositive();

    // return the range input child index
    // e.g. date_trunc(dt,'xxx') return 0
    int getMonotonicFunctionChildIndex();

    @Override
    default int getRangeInputChildIndex() {
        return getMonotonicFunctionChildIndex();
    }

    @Override
    default Optional<ColumnRange> inferRange(Literal lower, Literal upper, ExpressionRewriteContext context) {
        if (!isMonotonic(lower, upper)) {
            return Optional.empty();
        }
        return evaluateRangeEndpoints(lower, upper, context).flatMap(bounds -> isPositive()
                ? RangeInferable.createRange(bounds.first, bounds.second)
                : RangeInferable.createRange(bounds.second, bounds.first));
    }
}