Bug Report: select group_concat with order by causes failure

[joeyrivera]

Overview of the Issue

When we have a query that includes group_concat with an order by clause inside, we get a 2013 error. It runs fine in MySQL directly.

Reproduction Steps

Create table:

create table user_test(user_id bigint, name varchar(128), primary key(user_id));

Run query:

MYSQL

select group_concat(user_id order by name) from user_test;
+-------------------------------------+
| group_concat(user_id order by name) |
+-------------------------------------+
| NULL                                |
+-------------------------------------+
1 row in set (0.00 sec)

VITESS

select group_concat(user_id order by name) from user_test;
ERROR 2013 (HY000): Lost connection to MySQL server during query

Binary Version

vtgate --version
Version: 14.0.0-SNAPSHOT (Git revision 0fb472e99d branch 'main') built on Thu Mar 17 21:15:49 UTC 2022 by vitess@buildkitsandbox using go1.17.6 linux/amd64

Operating System and Environment details

cat /etc/os-release
PRETTY_NAME="Debian GNU/Linux 10 (buster)"
NAME="Debian GNU/Linux"
VERSION_ID="10"
VERSION="10 (buster)"
VERSION_CODENAME=buster
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"

uname -sr
Linux 5.10.47-linuxkit

uname -m
x86_64

Log Fragments

No response

[joeyrivera]

Note:

• the above query works in vtgate v12 and v13. Seems specific to v14:latest

[systay]

I would guess that the new aggregation sharding logic broke this in main

[systay]

@joeyrivera would it be possible to get a copy of your vtgate log? I'm guessing it will contain a stack trace.

Thanks a log for reporting this!

[joeyrivera]

I will circle back to this. I'm currently doing a bunch of v13 tests. When those are done, I'll go back to latest and test this.