PostgreSQL & regexp_split_to_array + unnest

I've that kind of string

我有那种弦

Test 1|new york| X, Test 2| chicago|Y, Test 3| harrisburg, pa| Z

测试1|纽约| X, 2|芝加哥|Y, 3|哈里斯堡，pa| Z

My required result it's

我需要的结果

 Column1  Column 2     Column3
 Test 1   new york        X
 Test 2   chicago         Y
 Test 3   harrisburg,pa   Z

But running this query

但运行该查询

SELECT  
split_part(stat.st, '|', 1) Column1,
split_part(stat.st, '|', 2) Column2,    
split_part(stat.st, '|', 3) Column3
FROM
(
    SELECT
            UNNEST (
                string_to_array('Test 1|new york| X, Test 2| chicago|Y, Test 3| harrisburg, pa| Z',',')
            )
         AS st
) stat;

Result is

结果是

 Column1  Column 2   Column3
 Test 1   new york      X
 Test 2   chicago       Y
 Test 3   harrisburg    
 pa          Z  

Column3 could be everything (except | ). Possible pattern to match it's .This could be repeated N times. STRING could be everything except | char.

Column3可以是一切(除了|)。可能的模式匹配它，这可以重复N次。字符串可以是除| char之外的所有东西。

How could I use regexp_split_to_array() to have my desire result set?

如何使用regexp_split_to_array()来设置我的愿望结果集?

1 个解决方案

#1

There is barely enough information to make this work. But this does the job:

几乎没有足够的信息使这个工作。但这确实起了作用:

SELECT * FROM crosstab3(
   $$
   SELECT (rn/3)::text AS x, (rn%3)::text, item
   FROM  (
      SELECT row_number() OVER () - 1 AS rn, trim(item) AS item
      FROM (
         SELECT CASE WHEN rn%2 = 1 THEN regexp_split_to_table(item, ',') 
                     ELSE item END AS item
         FROM  (
            SELECT row_number() OVER () AS rn, *
            FROM regexp_split_to_table('Test 1|new york| X, Test 2| chicago|Y, Test 3| harrisburg, pa| Z', '\|') AS item
            ) x
         ) y
      ) z
   $$)

Returns:

返回:

 row_name | category_1 |   category_2   | category_3
----------+------------+----------------+------------
 0        | Test 1     | new york       | X
 1        | Test 2     | chicago        | Y
 2        | Test 3     | harrisburg, pa | Z

After splitting the string at |, I build on the criterion that only lines with uneven row number shall be split at ,.
I trim() the results and add derivatives of another row_number() to arrive at this intermediary state before doing the cross tabulation:

在|上分割字符串后，我建立的条件是只有行数不均匀的行在，。我修剪()结果并添加另一个row_number()的导数，使其在做交叉表之前达到这个中间状态:

 x | text |      item
---+------+----------------
 0 | 0    | Test 1
 0 | 1    | new york
 0 | 2    | X
 1 | 0    | Test 2
 1 | 1    | chicago
 1 | 2    | Y
 2 | 0    | Test 3
 2 | 1    | harrisburg, pa
 2 | 2    | Z

Finally, I apply the crosstab3() function from the tablefunc module. To install it, if you haven't already:

最后，我从tablefunc模块中应用了crosstab3()函数。要安装它，如果你还没有:

CREATE EXTENSION tablefunc;

Pre-process with regexp_replace()

Here is an alternative that may be easier to comprehend. Not sure which is faster. Complex regular expressions tend to be expensive:

这里有一个更容易理解的选择。不知道哪个更快。复杂的正则表达式往往很昂贵:

SELECT trim(split_part(a,'|', 1)) AS column1
      ,trim(split_part(a,'|', 2)) AS column2
      ,trim(split_part(a,'|', 3)) AS column3
FROM  (
   SELECT unnest(
             string_to_array(
                         regexp_replace('Test 1|new york| X, Test 2| chicago|Y, Test 3| harrisburg, pa| Z'
                        ,'([^|]*\|[^|]*\|[^,]*),', '\1~^~', 'g'), '~^~')) AS a
   ) sub

This one replaces commas (,) only after two pipes (|), before proceeding.
Now using * instead of + to allow for empty strings between the pipes.

在继续之前，这一个只在两个管道(|)之后替换逗号。现在使用*而不是+来允许管道之间的空字符串。