Aurel/persist-graph: Mutate the graph in the background thread

[naure]

On top of #1023.

• Put each eye side into its own graph (with column graph_id).
  • Test SQL migrations (test_graph_migrations).
• Load the graph on startup (method load_graph_store).
  • Test of the loading (test_graph_load).
• Minimize code in server_hawk.rs.
• Consolidate with the iris store (same schema, same migrations scripts).
• Consolidate update of graph and iris store (same tx in server_hawk.rs).

[iliailia]

Could you merge it with main to have a better view of relevant changes?

[naure]

Could you merge it with main to have a better view of relevant changes?

Done.

[dkales]

I think this looks fine, just a design question:
Should we aim for the db insertion stuff to also be internal to the actor? This again would now add code that is unique to the CPU impl to the server_hawk.rs

[naure]

Good point to try to minimize change in server*.rs. As it stands the GraphStore needs a plain old data structure from the Hawk search, but a complex interaction with the startup, database update, and crash recovery mechanisms.

[iliailia]

Looks good to me so far.

[naure]

• Consolidate with the iris store (same schema).
• Consolidate update of graph and iris store (same tx).

Any opinions about this?

[iliailia]

• Consolidate with the iris store (same schema).
• Consolidate update of graph and iris store (same tx).

Any opinions about this?

Sounds like a good idea to me. It's a bit annoying to have both a graph and an iris store as arguments for any HNSW searcher method. Plus, semantically these two objects must relate to each other anyway.