Method unwrapSlotRef

fe/src/main/java/org/apache/impala/analysis/Expr.java:1709–1713

If 'this' is a SlotRef or a Cast that wraps a SlotRef, returns that SlotRef. Otherwise returns null.

(boolean implicitOnly)

   * Otherwise returns null.
   */
  public SlotRef unwrapSlotRef(boolean implicitOnly) {
    Expr unwrappedExpr = unwrapExpr(implicitOnly);
    if (unwrappedExpr instanceof SlotRef) return (SlotRef) unwrappedExpr;
    return null;
  }

  /**
   * Returns the first child if this Expr is a CastExpr or builtin cast