如何在BigQuery中使用UDF压缩Google Analytics自定义维度？

Question

根据Robert Sahlin的帖子,我想使用BigQuery UDF通过索引访问BigQuery中的任何Google Analytics自定义维度.在提议的解决方案中,Robert使用JavaScript UDF,我想知道是否可以对SQL UDF执行相同的操作 - 因为SQL UDF应该比JS UDF执行得更好.

建议的JS UDF:

CREATE TEMPORARY FUNCTION customDimensionByIndex(index INT64, arr ARRAY<STRUCT<index INT64, value STRING>>)
RETURNS STRING
LANGUAGE js AS """
  for (var j = 0; j < arr.length; j++){
    if(arr[j].index == index){
      return arr[j].value;
    }
  }
  """;

SELECT 
  fullvisitorId,
  visitId,
  hit.hitnumber,
  customDimensionByIndex(6, hit.customDimensions) as author,
  customDimensionByIndex(7, hit.customDimensions) as category 
FROM `123456.ga_sessions_YYYYMMDD`
JOIN
  UNNEST(hits) as hit?

Answer 1

使用SQL UDF:

#standardSQL
CREATE TEMP FUNCTION customDimensionByIndex(indx INT64, arr ARRAY<STRUCT<index INT64, value STRING>>) AS (
  (SELECT x.value FROM UNNEST(arr) x WHERE indx=x.index)
);

SELECT 
  fullvisitorId,
  visitId,
  hit.hitnumber,
  customDimensionByIndex(1, hit.customDimensions),
  customDimensionByIndex(2, hit.customDimensions),
  customDimensionByIndex(3, hit.customDimensions)
FROM `google.com:analytics-bigquery.LondonCycleHelmet.ga_sessions_20130910`, UNNEST(hits) hit
LIMIT 1000

我不确定为什么原始解决方案会在样本数据集上看到"命中"而不是"匹配"列 - 所以要获得单独的命中,我也必须使用UNNEST().