Transition from SQLite to PostgreSQL

[zhengqunkoo]

• Reading never blocks writing, and vice versa (MVCC concurrency resolution)
• Try out ArrayField for Coordinates
• PostGIS KDTree for Locations

[zhengqunkoo]

SQLite does not allow concurrent reads while writing to database. Combined with slow disk I/O, this makes the now service almost impossible to fulfill. By the time the writing connection to SQLite drops, it will likely be more than 5 minutes (i.e. now service will not have real-time data). Raising priority.

[zhengqunkoo]

MVCC likely prevents reading latest real-time data. Could isolate latest timestamps for now service from other timestamps for later service so now timestamps can be written quickly (making read data as recent as possible).