BigQuery：使用标准 SQL 的外部 UDF

Question

今天我尝试在 Web 编辑器 UI 中使用标准 SQL 语言编写 UDF，并且我已经取消选中“使用旧版 SQL”选项，但它返回给我以下错误消息： 未实现：您不能将旧版 SQL UDF 与标准 SQL 查询一起使用。见https://cloud.google.com/bigquery/docs/reference/standard-sql/migrating-from-legacy-sql#differences_in_user-defined_javascript_functions

因此我尝试了 Google Cloud Platform 上提供的外部 UDF 示例：https://cloud.google.com/bigquery/docs/reference/standard-sql/user-defined-functions。但它仍然返回给我同样的错误信息。在下面的例子中：

CREATE TEMPORARY FUNCTION multiplyInputs(x FLOAT64, y FLOAT64)
RETURNS FLOAT64
LANGUAGE js AS """
  return x*y;
""";
WITH numbers AS
  (SELECT 1 AS x, 5 as y
  UNION ALL
  SELECT 2 AS x, 10 as y
  UNION ALL
  SELECT 3 as x, 15 as y)
SELECT x, y, multiplyInputs(x, y) as product
FROM numbers;

问题：如何在 Web UI 中将外部 UDF 与标准 SQL 一起使用？

Answer 1

确保不在“UDF 编辑器”面板中输入输入。它应该与您的其余查询一起使用。示例见the topic in the migration guide：

#standardSQL
-- Computes the harmonic mean of the elements in 'arr'.
-- The harmonic mean of x_1, x_2, ..., x_n can be expressed as:
--   n / ((1 / x_1) + (1 / x_2) + ... + (1 / x_n))
CREATE TEMPORARY FUNCTION HarmonicMean(arr ARRAY<FLOAT64>)
  RETURNS FLOAT64 LANGUAGE js AS """
var sum_of_reciprocals = 0;
for (var i = 0; i < arr.length; ++i) {
  sum_of_reciprocals += 1 / arr[i];
}
return arr.length / sum_of_reciprocals;
""";

WITH T AS (
  SELECT GENERATE_ARRAY(1.0, x * 4, x) AS arr
  FROM UNNEST([1, 2, 3, 4, 5]) AS x
)
SELECT arr, HarmonicMean(arr) AS h_mean
FROM T;