SyncEngine Setup Updates Every Record in Synced Tables? Consider Custom Triggers?

[seanwoodward]

Does syncEngineSetup update every record in synced tables, SyncEngine.swift#L216?

If so, could affect other update triggers, like last modified date. Is it worthwhile to suggest considerations when creating custom triggers for synced tables?

[mbrandonw]

Hi @seanwoodward, good question and this is actually something I am working on right now.

Overall, people will need to update their triggers to play nicely with synchronization. There is a isUpdatingWithServerRecord function installed in your database connection (and made publicly available as a Swift function) that you can use to skip your triggers when we are doing things to the database. You could use it like so:

CREATE TEMPORARY TRIGGER "…"
AFTER UPDATE ON "…"
FOR EACH ROW WHEN NOT isUpdatingWithServerRecord()
BEGIN
  …
END

Or if you are using our trigger builder:

createTemporaryTrigger(
  "…",
  after: .delete { old in
    …
  } when: { _ in
    !isUpdatingWithServerRecord()
  }
)

This will make it so that our code can make updates to your tables without triggering your triggers. And we may rename this function in the near future. We named it when we thought it was an internal detail of the library, but now we see we need to publicize it.

However, that line specifically that you linked to is problematic. We are doing that mass update as a shortcut to mass enqueue saveRecord changes to the sync engine, and that does have the unfortunate side effect of invoking your triggers. So we will update that code to just enqueue the saveRecords directly.

Thanks!

[seanwoodward]

@mbrandonw Saw those, thanks. Should the the bool passes to withValue be true?

[mbrandonw]

Actually after merging that I realized that while we are now providing the tools publicly, that one line you linked to is still incorrect. Working on a correct solution to that specific problem now.

[seanwoodward]

looks like false might actually be appropriate for the sync engine triggers as implemented. look forward to the next set of changes.

[mbrandonw]

We think it's better to just not update the user tables at all during the initial upload to CloudKit. This PR https://github.com/pointfreeco/sharing-grdb-icloud/pull/14/files?w=1 does just that

[seanwoodward]

I think that sounds reasonable. I'll digest the update and chime in if anything jumps out.