Bug Report: exists may returns random result on a sharded table

[zengmin-wish]

Overview of the Issue

We found an issue with exists : I can't provide the exact query we use, but for the query like

select exists(select * from foo where some_field=some_value)

here foo is in a sharded keyspace, it seems if the inner query has result in one shard but have no result in another shard, then the outer query will return a random 0 or 1. Not sure if it is related, but for our particular query, the table is sharded on the field 'some_field', so if Vitess is smart enough, it doesn't need to send the query to all the shard.
We tried using gen4 planner, got the same result.

Reproduction Steps

See description.

Binary Version

v13.0.0

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/"

Log Fragments

No response

[frouioui]

Hello @zengmin-wish, we encountered a similar issue in the past (#9900). We fixed it on main (here) and on v13.0.1 (here). I see that you are running on v13.0.0, do you mind upgrading to v13.0.1 and letting us know if that solves your issue?

[GuptaManan100]

Hello @zengmin-wish, me and @systay were looking at this bug today, and we can confirm that this is an issue in all the three v13.0.0, v13.0.1 and main. The draft PR for the fix is here - #10152

[systay]

this issue is still not fixed for V3, and it needs to be backported. opening this again until that is done