fe/src/main/java/org/apache/impala/rewrite/BetweenToCompoundRule.java

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package org.apache.impala.rewrite;

import org.apache.impala.analysis.Analyzer;
import org.apache.impala.analysis.BetweenPredicate;
import org.apache.impala.analysis.BinaryPredicate;
import org.apache.impala.analysis.CompoundPredicate;
import org.apache.impala.analysis.Expr;
import org.apache.impala.analysis.Predicate;

/**
 * Rewrites BetweenPredicates into an equivalent conjunctive/disjunctive
 * CompoundPredicate.
 * It can be applied to pre-analysis expr trees and therefore does not reanalyze
 * the transformation output itself.
 * Examples:
 * A BETWEEN X AND Y ==> A >= X AND A <= Y
 * A NOT BETWEEN X AND Y ==> A < X OR A > Y
 */
public class BetweenToCompoundRule implements ExprRewriteRule {
  public static ExprRewriteRule INSTANCE = new BetweenToCompoundRule();

  @Override
  public Expr apply(Expr expr, Analyzer analyzer) {
    if (!(expr instanceof BetweenPredicate)) return expr;
    BetweenPredicate bp = (BetweenPredicate) expr;
    Expr result = null;
    if (bp.isNotBetween()) {
      // Rewrite into disjunction.
      Predicate lower = new BinaryPredicate(BinaryPredicate.Operator.LT,
          bp.getChild(0), bp.getChild(1));
      Predicate upper = new BinaryPredicate(BinaryPredicate.Operator.GT,
          bp.getChild(0), bp.getChild(2));
      result = new CompoundPredicate(CompoundPredicate.Operator.OR, lower, upper);
    } else {
      // Rewrite into conjunction.
      Predicate lower = new BinaryPredicate(BinaryPredicate.Operator.GE,
          bp.getChild(0), bp.getChild(1));
      Predicate upper = new BinaryPredicate(BinaryPredicate.Operator.LE,
          bp.getChild(0), bp.getChild(2));
      result = new CompoundPredicate(CompoundPredicate.Operator.AND, lower, upper);
    }
    return result;
  }

  private BetweenToCompoundRule() {}
}