Postgresql 和 jsonb : WHERE <a specific nested field in my json> IS NOT NULL

Question

表public.challenge，列行 JSONB

我的初始 JSON lines :

[
  {
    "line": 1,
    "blocs": [
      {
        "size": 100,
        "name": "abc"
      },
      {
        "size": 100,
        "name": "def"
      },
      {
        "size": 100,
        "name": "ghi"
      }
    ]
  },
  {
    "line": 2,
    "blocs": [
      {
        "size": 100,
        "name": "xyz"
      }
    ]
  }
]

期望的结果(为每个bloc添加一个新对象wrapper):

[
  {
    "line": 1,
    "blocs": [
      {
        "size": 100,
        "name": "abc",
        "wrapper": {
          "nestedName": "abc",
          "type": "regular"
        }
      },
      {
        "size": 100,
        "name": "def",
        "wrapper": {
          "nestedName": "def",
          "type": "regular"
        }
      },
      {
        "size": 100,
        "name": "ghi",
        "wrapper": {
          "nestedName": "ghi",
          "type": "regular"
        }
      }
    ]
  },
  {
    "line": 2,
    "blocs": [
      {
        "size": 100,
        "name": "xyz",
        "wrapper": {
          "nestedName": "xyz",
          "type": "regular"
        }
      }
    ]
  }
]

我有以下查询(来自 here ):

WITH cte AS (
   SELECT id_lines,
          jsonb_agg(
                  jsonb_set(val1, '{blocs}',
                      (
                        SELECT jsonb_agg(arr2 ||
                                         json_build_object(
                                             'wrapper', json_build_object('nestedName', arr2->'name', 'type', 'regular')
                                             )::jsonb
                            )
                        FROM jsonb_array_elements(arr1.val1->'blocs') arr2
                        WHERE arr2->'name' IS NOT NULL
                          )
                      ))
   FROM public.challenge, jsonb_array_elements(lines) arr1(val1)
   GROUP BY 1
)
UPDATE public.challenge SET lines=(cte.jsonb_agg) FROM cte
WHERE public.challenge.id_lines=cte.id_lines;

条件WHERE arr2->'name' IS NOT NULL不会过滤掉name为null的 block ，我很难找出原因..谢谢!

Answer 1

您必须区分 SQL NULL 和 JSON null。

IS NOT NULL 谓词测试 SQL NULL，这意味着该属性不存在于 JSON 中。

要测试 JSON null，请使用

WHERE arr2->'name' <> 'null'::jsonb

类型转换为 jsonb 是不必要的，并且会隐式执行。