message: Use is_some() instead of count()
diff: @@ -165,7 +165,7 @@ fn check_expr<'a, T: 'static + Debug>(
  Ok(negated ^ (evaluate(low)? <= target && target <= evaluate(high)?))
  }
  - Expr::Exists(expr) => Ok(select(storage, expr, filter_context)?.count() > 0),
  + Expr::Exists(expr) => Ok(select(storage, expr, filter_context)?.next().is_some()),
  _ => Err(FilterError::Unimplemented.into()),
  }
  }
  