New Journal Store Schema

[octonato]

The new journal store table will have a few more fields:

• ser_id (Int)
• ser_manifest (String)
• event_manifest (String)
• event_payload (String)
• writer_uuid (String)
• timestamp column (see #28383). Useful for metrics about read-side processors lagging. The timestamp will be addes as Long and defaulting to 0.

We need to refactor the Journal DAO for that new format.

The current table is called journal. Instead of altering it, we will design a new table structure and call it journal_messages. New users can just start using it from version 4.0.0 onward. Existing users will need to run the migration procedure to copy their data from journal to journal_messages.

ByteArrayJournalSerializer should be moved to the migration module as we will need it for running migrations (reading old data from the journal table).

Next to the journal table, we need a tags table. There is a one-to-many relation between the two tables. One event can have zero or more tags.

The Journal DAO must take this into account and execute inserts on both tables atomically.

Events by tag queries need to be refactored to consider the new tags table.

[patriknw]

maybe call it journal_events instead of journal_messages? Akka Persistence naming of these things as messages is wrong in my opinion, but we don't have to replicate that problem to more places than necessary.

[octonato]

Good. I confess that I was trying to align as much as possible. Cassandra calls it message while Couchbase is using journal_message in the singular.

[PerWiklander]

Aren't SQL tables typically named in the singular?

[chbatey]

We also need to add columns for the metadata

[chbatey]

#467