feat(dbal): insert ignore conflict method for MySQL and SQLite

[Altahrim]

Summary

Add ignore conflicts method for MySQL
Similar to PgSQL: https://github.com/nextcloud/server/blob/master/lib/private/DB/AdapterPgSql.php#L26-L37

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[Altahrim]

Actually, there is a different behaviour with PostgreSQL…

• MySQL will update the duplicated rows with values from the insert
• PostgreSQL will ignore the new values for duplicated rows.

I see two solutions:

• We can mimic the behaviour of PostgreSQL in MySQL by updating only the primary key (but at this point we don't know the primary key). It will do nothing.
• Or we may want to create a new method instead which will update the duplicate rows with new values for both storage engines, but I don't know if it's possible to do the same with Oracle

[come-nc]

On conflict this ones updates the row while pgsql implementation will not touch it, no?

[Altahrim]

On conflict this ones updates the row while pgsql implementation will not touch it, no?

Yep, see above comment :)

[solracsf]

On conflict this ones updates the row while pgsql implementation will not touch it, no?

Can this be an option?
https://mariadb.com/kb/en/insert-ignore/

[Altahrim]

Can this be an option?
mariadb.com/kb/en/insert-ignore

For me it ignores too many errors. I would prefer to avoid this.

[Altahrim]

Finally, it seems INSERT IGNORE is the only way to achieve this with our current setup of MySQL.

From MySQL documentation

With ON DUPLICATE KEY UPDATE, the affected-rows value per row is 1 if the row is inserted as a new row, 2 if an existing row is updated, and 0 if an existing row is set to its current values. If you specify the CLIENT_FOUND_ROWS flag to the mysql_real_connect() C API function when connecting to mysqld, the affected-rows value is 1 (not 0) if an existing row is set to its current values.

The other way is to update all fields instead of ignore them but I failed to achieve this with Oracle. It's sad because it could make sense when we launch an update after the insertIgnoreConflict

[Altahrim]

@nickvergessen Do you think it is a correct solution given the risks of ignoring other errors?

[come-nc]

A unit test would be nice