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// to you under the Apache License, Version 2.0 (the
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//
//   http://www.apache.org/licenses/LICENSE-2.0
//
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package org.apache.doris.rewrite;

import org.apache.doris.analysis.Analyzer;
import org.apache.doris.analysis.BinaryPredicate;
import org.apache.doris.analysis.BoolLiteral;
import org.apache.doris.analysis.CompoundPredicate;
import org.apache.doris.analysis.Expr;
import org.apache.doris.analysis.SlotRef;
import org.apache.doris.common.AnalysisException;

/**
 * Normalizes binary predicates of the form <expr> <op> <slot> so that the slot is
 * on the left hand side. Predicates where <slot> is wrapped in a cast (implicit or
 * explicit) are normalized, too.
 *
 * Examples:
 * 5 > id -> id < 5
 */
public class NormalizeBinaryPredicatesRule implements ExprRewriteRule {
    public static ExprRewriteRule INSTANCE = new NormalizeBinaryPredicatesRule();

    @Override
    public Expr apply(Expr expr, Analyzer analyzer) throws AnalysisException {
        if (!(expr instanceof BinaryPredicate)) return expr;
        if (expr.getChild(0).unwrapSlotRef(false) != null) return expr;
        if (expr.getChild(1).unwrapSlotRef(false) == null) return expr;

        BinaryPredicate.Operator op = ((BinaryPredicate) expr).getOp();

        return new BinaryPredicate(op.converse(), expr.getChild(1), expr.getChild(0));
    }
}
