Function ModifyExpression

cpp/src/arrow/compute/util.h:138–172

/// argument. If no arguments were modified the unmodified Expression* will be nullptr.
template <typename PreVisit, typename PostVisitCall>
Result<Expression> ModifyExpression(Expression expr, const PreVisit& pre,
                                    const PostVisitCall& post_call) {
  ARROW_ASSIGN_OR_RAISE(expr, Result<Expression>(pre(std::move(expr))));

  auto call = expr.call();
  if (!call) return expr;

  bool at_least_one_modified = false;
  std::vector<Expression> modified_arguments;

  for (size_t i = 0; i < call->arguments.size(); ++i) {
    ARROW_ASSIGN_OR_RAISE(auto modified_argument,
                          ModifyExpression(call->arguments[i], pre, post_call));

    if (Expression::Identical(modified_argument, call->arguments[i])) {
      continue;
    }

    if (!at_least_one_modified) {
      modified_arguments = call->arguments;
      at_least_one_modified = true;
    }

    modified_arguments[i] = std::move(modified_argument);
  }

  if (at_least_one_modified) {
    // reconstruct the call expression with the modified arguments
    auto modified_call = *call;
    modified_call.arguments = std::move(modified_arguments);
    return post_call(Expression(std::move(modified_call)), &expr);
  }

  return post_call(std::move(expr), NULLPTR);
}

// Helper class to calculate the modified number of rows to process using SIMD.
//