MySQL Bugs: #120360: Feature Request to add parameter to raise an error when group_concat_max

Bug #120360	Feature Request to add parameter to raise an error when group_concat_max_len exceeeds
Submitted:	28 Apr 4:54	Modified:	28 Apr 11:49
Reporter:	Tsubasa Tanaka (OCA)	Email Updates:
Status:	Open	Impact on me:	None
Category:	MySQL Server: Errors	Severity:	S4 (Feature request)
Version:	9.7.0	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
Currently, GROUP_CONCAT raise a warning when group_concat_max_len exceeds.

```
mysql97 208136> SHOW WARNINGS;
+---------+------+-----------------------------------+
| Level   | Code | Message                           |
+---------+------+-----------------------------------+
| Warning | 1260 | Row 284 was cut by GROUP_CONCAT() |
+---------+------+-----------------------------------+
1 row in set (0.001 sec)
```

This feature-request is adding parameter to raise an error instead of raising a warning.

How to repeat:
SQL

```
WITH RECURSIVE v AS (SELECT 1 AS n UNION ALL SELECT n + 1 AS n FROM v WHERE n < 1000) SELECT GROUP_CONCAT(n) FROM v\G
```

Now,

```
1 row in set, 1 warning (0.001 sec)

mysql97 208136> SHOW WARNINGS;
+---------+------+-----------------------------------+
| Level   | Code | Message                           |
+---------+------+-----------------------------------+
| Warning | 1260 | Row 284 was cut by GROUP_CONCAT() |
+---------+------+-----------------------------------+
1 row in set (0.001 sec)
```

I hope

```
ERROR 1260 (HY000): Row 284 was cut by GROUP_CONCAT()
```

Suggested fix:
- Adding new parameter ex. --group-concat-max-len-abort 
- Adding if condition where call push_warning_printf with ER_CUT_VALUE_GROUP_CONCAT.
  - https://github.com/search?q=repo%3Amysql%2Fmysql-server%20ER_CUT_VALUE_GROUP_CONCAT&type=c...

Add strict_group_concat to raise error (*) I confirm the code being submitted is offered under the terms of the OCA, and that I am authorized to contribute it.

Contribution: bug120360_strict_group_concat.patch (application/octet-stream, text), 2.87 KiB.

After patch, strict_group_concat = {ON|OFF} is there and handling warning or error.

```
mysql97 10> SELECT @@session.strict_group_concat;
+-------------------------------+
| @@session.strict_group_concat |
+-------------------------------+
|                             0 |
+-------------------------------+
1 row in set (0.000 sec)

mysql97 10> WITH RECURSIVE v AS (SELECT 1 AS n UNION ALL SELECT n + 1 AS n FROM v WHERE n < 1000) SELECT GROUP_CONCAT(n) FROM v\G
*************************** 1. row ***************************
GROUP_CONCAT(n): 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181,182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,198,199,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,216,217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,234,235,236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251,252,253,254,255,256,257,258,259,260,261,262,263,264,265,266,267,268,269,270,271,272,273,274,275,276,277,278,279,280,281,282,283,
1 row in set, 1 warning (0.001 sec)

mysql97 10> SHOW WARNINGS;
+---------+------+-----------------------------------+
| Level   | Code | Message                           |
+---------+------+-----------------------------------+
| Warning | 1260 | Row 284 was cut by GROUP_CONCAT() |
+---------+------+-----------------------------------+
1 row in set (0.000 sec)

mysql97 10> SET SESSION strict_group_concat = ON;
Query OK, 0 rows affected (0.000 sec)

mysql97 10> WITH RECURSIVE v AS (SELECT 1 AS n UNION ALL SELECT n + 1 AS n FROM v WHERE n < 1000) SELECT GROUP_CONCAT(n) FROM v\G
ERROR 1260 (HY000): Row 284 was cut by GROUP_CONCAT()
```