BigQuery支持哪些JsonPath表达式?

为了克服JsonPath的BigQuery“限制”,可以引入 custom function
注意:它使用jsonpath-0.8.0。js,可从 https://code.google.com/archive/p/jsonpath/downloads

#standardSQL
CREATE TEMPORARY FUNCTION CUSTOM_JSON_EXTRACT(json STRING, json_path STRING)
RETURNS STRING
LANGUAGE js AS """
    try { var parsed = JSON.parse(json);
        return JSON.stringify(jsonPath(parsed, json_path));
    } catch (e) { return null }
"""
OPTIONS (
    library="gs://your_bucket/jsonpath-0.8.0.js"
);
WITH t AS (
SELECT '''
{ "store": {
        "book": [ 
            { "category": "reference",
                "author": "Nigel Rees",
                "title": "Sayings of the Century",
                "price": 8.95
            },
            { "category": "fiction",
                "author": "Evelyn Waugh",
                "title": "Sword of Honour",
                "price": 12.99
            },
            { "category": "fiction",
                "author": "Herman Melville",
                "title": "Moby Dick",
                "isbn": "0-553-21311-3",
                "price": 8.99
            },
            { "category": "fiction",
                "author": "J. R. R. Tolkien",
                "title": "The Lord of the Rings",
                "isbn": "0-395-19395-8",
                "price": 22.99
            }
        ],
        "bicycle": {
            "color": "red",
            "price": 19.95
        }
    }
}
''' AS x
)
SELECT 
    CUSTOM_JSON_EXTRACT(x, '$.store.book[*].author'),
    CUSTOM_JSON_EXTRACT(x, '$..*[?(@.price==22.99)].author'),
    CUSTOM_JSON_EXTRACT(x, '$..author'),
    CUSTOM_JSON_EXTRACT(x, '$.store.*'),
    CUSTOM_JSON_EXTRACT(x, '$.store..price'),
    CUSTOM_JSON_EXTRACT(x, '$..book[(@.length-1)]'),
    CUSTOM_JSON_EXTRACT(x, '$..book[-1:]'),
    CUSTOM_JSON_EXTRACT(x, '$..book[0,1]'),
    CUSTOM_JSON_EXTRACT(x, '$..book[:2]'),
    CUSTOM_JSON_EXTRACT(x, '$..book[?(@.isbn)]')
FROM t

结果如下

CUSTOM_JSON_EXTRACT(x, '$.store.book[*].author')

[
  "Nigel Rees"
  "Evelyn Waugh"
  "Herman Melville"
  "J. R. R. Tolkien"
]

对于 CUSTOM_JSON_EXTRACT(x, '$..*[?(@.price==22.99)].author')

[
  "J. R. R. Tolkien"
]  

CUSTOM_JSON_EXTRACT(x, '$.store..price')

[
  8.95
  12.99
  8.99
  22.99
  19.95
]

等等

支持的元素位于链接到的节的表中。具体来说,它包括 $ , . [] ,其中后者可以是子运算符或下标(数组)运算符。如果未列出,则不支持。