@Paladox update?

In T4425#130025, @John wrote:

@Paladox update?

I'm not sure if this is safe to do hence why I've set this on the low priority.

I could copy a db which is in a foreign language and try and convert it and see if it works.

@RhinosF1 did the db person from the wmf get back to you?

@RhinosF1 said they use mediawikis default.

@Southparkfan I'm wondering if I could have assistance on this please? This is a really big change and could lead to data loss.

@Southparkfan See the above please

In T4425#142254, @John wrote:

@Southparkfan See the above please

I would like to assist here, but I am not very experienced with character sets. I have a few questions though.

• Shouldn't we migrate from latin1 (our MariaDB default) to binary (MediaWiki default), instead from latin1 to utf8mb4? (see also next question)
• T4425#137259: didn't they use binary?
• Do you have a conversion procedure in mind? What are the known caveats?
• Are other systems (Matomo, Phabricator, etc.) running on non-supported character sets too?
• Is read-only mode required for converting (read: can pt-osc handle this conversion for us without read-only mode enabled)? If so, what is the ETA?
• Are things going to explode if one wiki has binary tables, whereas another wiki has latin1 tables? Data corruption is likely and will have a major impact.
• Suggestion: we must back-up wikis prior to converting the tables.
• Suggestion: a Wikimedia DBA could help you answering these questions. They are very experienced with the MediaWiki database architecture.

Discussed; paladox will contact Wikimedia DBAs.

https://phabricator.wikimedia.org/T250058#6051265 suggests search will break when converting to binary?

Spoked with a DBA at wmf briefly (Marostegui). He said it uses utf8mb4 and binary. Also he said he guessed it required read only and also alter table commands.

He also said he doesn't think it would cause corruption if one table had latin1 and the other binary but he also said it's worth checking out.

Phabricator uses utf8mb4 (as it's forced).

Also:

MariaDB [metawiki]> show table status like 'searchindex';
+-------------+--------+---------+------------+-------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+-----------------+----------+----------------+---------+------------------+-----------+
| Name        | Engine | Version | Row_format | Rows  | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time         | Update_time         | Check_time | Collation       | Checksum | Create_options | Comment | Max_index_length | Temporary |
+-------------+--------+---------+------------+-------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+-----------------+----------+----------------+---------+------------------+-----------+
| searchindex | InnoDB |      10 | Dynamic    | 20670 |           2004 |    41435136 |               0 |       425984 |   4194304 |           NULL | 2020-07-15 23:25:09 | 2021-06-02 11:40:55 | NULL       | utf8_general_ci |     NULL |                |         |                0 | N         |
+-------------+--------+---------+------------+-------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+-----------------+----------+----------------+---------+------------------+-----------+

I wonder if that should be moved to utf8mb4_unicode_ci?