embedder: created high-watermark table, refactor about parabol

[jordanh]

It also occurred to me that there could be an alternative way to solve this... we don't allow the app to add items to the EmbeddedMetadata table unless all the history has been added first.

The indexing process is a one-shot. After all the history is added, the refreshment doesn't need to happen again.

[mattkrick]

absolutely! the trick is what to do with the jobs coming from the app.

if we treated this as a migration, you could run the migration & then update the app, but we'd miss the jobs that happened in the seconds between the migration & the app starting.

we could do a 2-phase rollout:

• part 1 updates the app so all new items get added to metadata table
• part 2 is a migration that grabs the end = min(oldest date, r.maxval) for that metadata type in the metadata table and then processes history for r.minval, end.

[jordanh]

I think we decided to tackle this a different way, so I'll close this for now