arrays - pq: 函数 unnest(unknown) 不是唯一的

Question

以下代码运行良好。但我想将 array['a', 'b', 'c', 'd', 'e'] 定义为变量。

rows, err :=  db.Query("select colname from (SELECT date, unnest(array['a', 'b', 'c', 'd', 'e']) AS colname, unnest(array[a, b, c, d, e]) AS thing from test1 where date='123') as tester where thing=1;")

所以我尝试使用 github.com/lib/pq 跟踪代码。

arr1 := []string{"a", "b", "c", "d", "e"}      
rows, err :=  db.Query("select colname from (SELECT date, unnest($1) AS colname, unnest($1) AS thing from test1 where date='123') as tester where thing=1;", pq.Array(arr1))

但是出现类似“pq: function unnest(unknown) is not unique”的错误。 表结构和示例数据--

test=# \d+ test1
                                Table "public.test1"
 Column |         Type          | Modifiers | Storage  | Stats target | Description 
--------+-----------------------+-----------+----------+--------------+-------------
 a      | character varying(10) |           | extended |              | 
 b      | character varying(10) |           | extended |              | 
 c      | character varying(10) |           | extended |              | 
 d      | character varying(10) |           | extended |              | 
 e      | character varying(10) |           | extended |              | 
 date   | character varying(10) |           | extended |              | 

test=# select * from test1 ;
 a | b | c | d | e | date 
---+---+---+---+---+------
 3 | 1 | 3 | 2 | 3 | 124
 3 | 3 | 2 | 2 | 1 | 125
 1 | 2 | 2 | 1 | 3 | 126
 1 | 2 | 3 | 2 | 3 | 127
 1 | 1 | 2 | 2 | 3 | 123
(5 rows)

基本上我想要列名称(a、b、c、d 或 e)在任何特定日期的值为“1”。

Answer 1

我猜想 pq.Array 给你一个字符串形式的 PostgreSQL 数组，所以你最终得到这样的东西:

unnest('{a,b,c,d,e}')

并且 PostgreSQL 不确定它应该如何解释该字符串，因此提示 unnest(unknown)。您应该能够添加一个明确的类型转换来清除问题:

unnest($1::text[])         -- PostgreSQL-specific casting syntax
unnest(cast($1 as text[])) -- Standard casting syntax

你最终会得到这样的结果:

rows, err :=  db.Query("select colname from (SELECT date, unnest($1::text[]) AS colname, unnest($1) AS thing from test1 where date='123') as tester where thing=1;", pq.Array(arr1))