BigQuery - JSONpath 递归运算符 (2/2)

Question

在没有显然不受支持的运算符“..”的情况下，有什么方法可以在 BigQuery 中实现对 JSON 字符串对象的递归搜索吗？

动机：仅当位于下面的“学生”中时才访问“姓名”。

查询

SELECT JSON_EXTRACT(json_text, '$..students.name') AS first_student
FROM UNNEST([
'{"class" : {"students" : {"name" : "Jane"}}}'
]) AS json_text;

期望输出

+-----------------+
| first_student   |
+-----------------+
| "Jane"          |
+-----------------+

当前输出

JSON路径中不支持的运算符：..

Answer 1

Is there any way to realize a recursive search on a JSON string object in BigQuery in absence of the operator "..", which is apparently not supported ?

考虑以下方法

CREATE TEMPORARY FUNCTION CUSTOM_JSON_EXTRACT(json STRING, json_path STRING)
RETURNS STRING 
LANGUAGE js AS """
  return jsonPath(JSON.parse(json), json_path);
"""
OPTIONS (
  library="gs://some_bucket/jsonpath-0.8.0.js"
);
SELECT CUSTOM_JSON_EXTRACT(json_text, '$..students.name') AS first_student
FROM UNNEST([
'{"class" : {"students" : {"name" : "Jane"}}}'
]) AS json_text;

有输出

注意：为了克服当前 BigQuery 对 JsonPath 的“限制”，上述解决方案使用 UDF + 外部库 - jsonpath-0.8.0.js 可以从 https://code.google.com/archive/p/jsonpath/downloads 下载并上传到 Google Cloud Storage - gs://some_bucket/jsonpath-0.8.0.js

BigQuery - JSONpath 递归运算符 (2/2)

BigQuery - JSONpath recursive operator (2/2)

jsonpath

google-bigquery

google-cloud-platform