如何在JSON数组中找到元素的索引（PostgreSQL 9.3）？

Question

我在表格radio responses有一些数据我正在聚合，看起来像这样：

SELECT question_id, arr FROM radio_responses;

  question_id |       arr       
-------------+-----------------
          73 | [1,0,0]
          73 | [1,0,0]
          73 | [0,1,0]
          73 | [0,1,0]
          73 | [0,1,0]
          73 | [0,0,1]
          73 | [0,1,0]
          73 | [0,1,0]
          73 | [0,0,1]
          73 | [0,0,1]
          73 | [1,0,0]
          74 | [1,0]
          74 | [0,1]
          74 | [1,0]
          74 | [0,1]
          74 | [1,0]
          74 | [0,1]
          77 | [0,1]
          77 | [0,1]
          77 | [0,1]

我的最终目标是从每个数组中提取1的索引。 我找不到任何使用JSON类型的函数，但是如果我有一个int[]数组，我确实发现我可以使用idx() 。

我已经尝试了各种解决方案，但它们似乎都依赖于首先取消数据，这似乎是不必要的，特别是因为信息在这个过程中丢失了（除非有一些东西使用了我错过的WITH ORDINALITY ）。

我正在使用Postgres 9.3版。

Answer 1

您的问题实际上与RDBMS无关。 但是，如果您不想使用取消等等，并且如果您坚持使用9.3版本：

create or replace function json_array_position(a json, e int) returns int language plpythonu stable as $$
  import json;
  r = json.loads(a)
  return r.index(e)
$$;

select json_array_position('[1,2,3]'::json, 2);

Answer 2

select      *
          ,(select min(i) + 1
            from   generate_series(0,json_array_length(arr)-1) as gs (i)
            where  (arr->>i)::int = 1
            )                           as ind

from        radio_responses
;

---

+-------------+---------+-----+
| question_id | arr     | ind |
+-------------+---------+-----+
| 73          | [1,0,0] | 1   |
+-------------+---------+-----+
| 73          | [1,0,0] | 1   |
+-------------+---------+-----+
| 73          | [0,1,0] | 2   |
+-------------+---------+-----+
| 73          | [0,1,0] | 2   |
+-------------+---------+-----+
| 73          | [0,1,0] | 2   |
+-------------+---------+-----+
| 73          | [0,0,1] | 3   |
+-------------+---------+-----+
| 73          | [0,1,0] | 2   |
+-------------+---------+-----+
| 73          | [0,1,0] | 2   |
+-------------+---------+-----+
| 73          | [0,0,1] | 3   |
+-------------+---------+-----+
| 73          | [0,0,1] | 3   |
+-------------+---------+-----+
| 73          | [1,0,0] | 1   |
+-------------+---------+-----+
| 74          | [1,0]   | 1   |
+-------------+---------+-----+
| 74          | [0,1]   | 2   |
+-------------+---------+-----+
| 74          | [1,0]   | 1   |
+-------------+---------+-----+
| 74          | [0,1]   | 2   |
+-------------+---------+-----+
| 74          | [1,0]   | 1   |
+-------------+---------+-----+
| 74          | [0,1]   | 2   |
+-------------+---------+-----+
| 77          | [0,1]   | 2   |
+-------------+---------+-----+
| 77          | [0,1]   | 2   |
+-------------+---------+-----+
| 77          | [0,1]   | 2   |
+-------------+---------+-----+