PostgreSQL JSONB查询每个键的类型

Posted 2021-04-03

我有一张桌子：

CREATE TABLE x(
  id BIGSERIAL PRIMARY KEY,
  data JSONB 
);
INSERT INTO x(data) 
VALUES( '{"a":"test", "b":123, "c":null, "d":true}' ),
      ( '{"a":"test", "b":123, "c":null, "d":"yay", "e":"foo", "f":[1,2,3]}' );

如何查询该表中每个键的类型，因此它会给出如下输出：

a | string:2 
b | number:2
c | null:2
d | boolean:1 string:1
e | string:1 
f | jsonb:1 -- or anything

我只知道获取密钥和计数的方法，但不知道如何获取每个密钥的类型：

SELECT jsonb_object_keys(data), COUNT(id) FROM x GROUP BY 1 ORDER BY 1

这将给出类似的东西：

a |  2
b |  2
c |  2
d |  2
e |  1
f |  1

答案

编辑：

正如pozs指出的那样，有两个typeof函数：一个用于JSON，一个用于SQL。此查询是您正在寻找的查询：

SELECT
    json_data.key,
    jsonb_typeof(json_data.value),
    count(*)
FROM x, jsonb_each(x.data) AS json_data
group by key, jsonb_typeof
order by key, jsonb_typeof;

旧答案:(嘿，它有效...）

此查询将返回键的类型：

SELECT
    json_data.key,
    pg_typeof(json_data.value),
    json_data.value
FROM x, jsonb_each(x.data) AS json_data;

...不幸的是，你会注意到Postgres没有区分不同的JSON类型。它将它全部视为jsonb，因此结果如下：

 key1 | value1 |   value   
------+--------+-----------
 a    | jsonb  | "test"
 b    | jsonb  | 123
 c    | jsonb  | null
 d    | jsonb  | true
 a    | jsonb  | "test"
 b    | jsonb  | 123
 c    | jsonb  | null
 d    | jsonb  | "yay"
 e    | jsonb  | "foo"
 f    | jsonb  | [1, 2, 3]
(10 rows)

然而，没有那么多的JSON primitive types，输出似乎是明确的。所以这个查询会做你想要的：

with jsontypes as (
    SELECT
        json_data.key AS key1,
        CASE WHEN left(json_data.value::text,1) = '"'  THEN 'String'
             WHEN json_data.value::text ~ '^-?\d' THEN
                CASE WHEN json_data.value::text ~ '\.' THEN 'Number'
                     ELSE 'Integer'
                END
             WHEN left(json_data.value::text,1) = '['  THEN 'Array'
             WHEN left(json_data.value::text,1) = '{'  THEN 'Object'
             WHEN json_data.value::text in ('true', 'false')  THEN 'Boolean'
             WHEN json_data.value::text = 'null'  THEN 'Null'
             ELSE 'Beats Me'
        END as jsontype
    FROM x, jsonb_each(x.data) AS json_data -- Note that it won't work if we use jsonb_each_text here because the strings won't have quotes around them, etc.
)
select *, count(*) from jsontypes
group by key1, jsontype
order by key1, jsontype;

输出：

 key1 | jsontype | count 
------+----------+-------
 a    | String   |     2
 b    | Integer  |     2
 c    | Null     |     2
 d    | Boolean  |     1
 d    | String   |     1
 e    | String   |     1
 f    | Array    |     1
(7 rows)

另一答案

您可以使用jsonb_typeof改进上一个查询

with jsontypes as (
    SELECT
        json_data.key AS key1,
        jsonb_typeof(json_data.value) as jsontype
    FROM x, jsonb_each(x.data) AS json_data
)
select *, count(*)
from jsontypes
group by 1, 2
order by 1, 2;