KB-1115 GROUP_CONCAT function in MySQL truncates value

Parmida Borhani — Thu, 09 Aug 2018 02:12:29 GMT

Current Revision posted to Appian Knowledge Base by Parmida Borhani on 8/9/2018 2:12:29 AM

Symptoms

When a view is using GROUP_CONCAT function, the value is truncated in MySQL.

Cause

Mysql truncates to the maximum length that is given by the group_concat_max_len system variable, which is a default value of 1024 bytes.

For more information, refer to MySQL Documentation - GROUP_CONCAT(expr).

Action

To resolve this issue, use one of the following options:

For only self-managed installations, change the value of group_concat_max_len at runtime by doing the following (val is an unsigned integer):
```
SET [GLOBAL | SESSION] group_concat_max_len = val; 
```

For both self-managed installations and cloud sites, modify the SQL for the view using a combination of CONCATand GROUP_CONCAT.

Original Query:

SELECT GROUP_CONCAT(last_name) FROM employee

Modified Query:

SELECT   SUBSTRING(     CONCAT(       GROUP_CONCAT(         IF(employee_id BETWEEN 1 AND 100, CONCAT(',', last_name), '')         SEPARATOR ''       ),       GROUP_CONCAT(         IF(employee_id BETWEEN 101 AND 200, CONCAT(',', last_name), '')         SEPARATOR ''       )     ),     2   ) AS result FROM employee

Affected Versions

This article applies to all versions of Appian.

Last Reviewed: April 2016

Tags: database, mysql, infrastructure