Pascal Precht d0e0deac95 feat: introduce discord_message_authors persistence APIs
This introduces a new table to store discord message authors.
The main reason this table is being introduce is so that we don't have
to duplicate discord message author information in the `user_messages`
table when importing discord communities (ongoing work).

In addition to the table there are also two new APIs on the messenger
persistence layer (which are later used in the import logic):

- `HasDiscordMessageAuthor`
- `SaveDiscordMessageAuthor`

Closes #2759
2022-08-10 10:13:55 +02:00
..
2020-01-10 19:59:01 +01:00
2020-01-10 19:59:01 +01:00
2020-04-16 15:51:28 +02:00
2021-01-08 08:43:16 +01:00

How to write migrations?

We only write up migrations, down migrations are not always possible in sqlite or too complex/too expensive. For example to remove a column you would have to duplicate the table, copy over the data, delete and recreated. This can be very expensive for some tables (user_messages for example), so should not be attempted.

Notes

One issue we faced multiple times is that updates to user_messages can be very expensive, leading to slow upgrade times and interrupted migrations. So avoid writes if not necessary.