VRep JSON Columns: fix bug where vreplication of update statements were failing

[rohit-nayak-ps]

Description

During vreplication we set the MySQL connection to use binary charsets. Due to unexpected MySQL behavior, with collations and json columns, like: https://bugs.mysql.com/bug.php?id=93052, we need to cast json columns to utf8mb4.. We had done this as part of #6829. It turns out however that the casting was only done for inserts on the target and not for updates.

The copy phase results only in (bulk) inserts, so any updates done before we do the copy will not face this issue. This bug surfaces only if the updates are done while we stream binlog events: during the catchup, fastforward or replicate phases.

This PR adds the casting convert(<value> as utf8mb4) while building update plans as well. The only non-test code change is here: https://github.com/vitessio/vitess/pull/7640/files#diff-944642971422bb00ed68466f784f8b586f5e800f57e0c46002d6194c517cb1a0

Signed-off-by: Rohit Nayak rohit@planetscale.com

Related Issue(s)

https://github.com/planetscale/vitess-private/issues/101

Checklist

• Should this PR be backported?
• Tests were added or are not required
• Documentation was added or is not required

Impacted Areas in Vitess

Components that this PR will affect:

• Query Serving
• VReplication
• Cluster Management
• Build/CI
• VTAdmin

[deepthi]

We should be testing mysql80 as well.

[deepthi]

If this is something that doesn't work only on percona56, we should exclude just that one flavor.

[rohit-nayak-ps]

Added mysql80 in addition to mysql57. The Percona flavor is mysql56 and other platforms start with mariadb.

[deepthi]

LGTM

[williamsjasonj]

I believe I am still hitting this same issue running this version (Git revision 873d89a branch 'master') built on Thu Mar 11 09:16:17 UTC 2021
I have a few tables that have a json data type. When running vreplication, the table itself replicates fine, but any updates to that table throw this error "Cannot create a JSON value from a string with CHARACTER SET 'binary'" and vreplication breaks.

[rohit-nayak-ps]

That commit seems to have been made one minute before the merge of this PR. Can you please try again with the latest code?

rohit@rohit-ubuntu:~/vitess-ps/go/test/endtoend/vreplication$ git checkout 2726c84e0b9c1eb10fe76701bf447348a01562ad
Previous HEAD position was 873d89a57 Merge pull request #7639 from AdamKorcz/fuzz1
HEAD is now at 2726c84e0 Merge pull request #7640 from planetscale/rn-json-collation-bug
rohit@rohit-ubuntu:~/vitess-ps/go/test/endtoend/vreplication$ git log
commit 2726c84e0b9c1eb10fe76701bf447348a01562ad (HEAD)
Merge: 873d89a57 a0f7933ed
Author: Deepthi Sigireddi <deepthi@planetscale.com>
Date:   Tue Mar 9 08:06:05 2021 -0800

    Merge pull request #7640 from planetscale/rn-json-collation-bug
    
    VRep JSON Columns: fix bug where vreplication of update statements were failing

commit 873d89a57839c7e1ea1ec12544a8c04add6271b7
Merge: 2d82b0066 00910c657
Author: Andres Taylor <andres@planetscale.com>
Date:   Tue Mar 9 17:05:03 2021 +0100

    Merge pull request #7639 from AdamKorcz/fuzz1
    
    Fuzzing: Add 3 fuzzers for mysql endpoints

[williamsjasonj]

Thanks! I am now running Version: 10.0.0-SNAPSHOT (Git revision de902e5 branch 'master') built on Mon Mar 15 19:02:59 UTC 2021 by vitess@d7b8a3c04182 using go1.15.6 linux/amd64
I had to restart the vreplication process, so it will take a day or two before I know if this fix works.

[williamsjasonj]

Fix is tested - replication of updates to JSON data types is confirmed!