The LSIF processes store most of their data in SQLite repositories on a shared disk that are written once by a worker on LSIF dump upload, and read many times by the APIs to answer LSIF/LSP queries. Cross-repository and commit graph data is stored in Postgres, as this database requires many concurrent writers (which is an unsafe operation for SQLite in a networked application). The LSIF processes retrieve PostgreSQL connection configuration from the frontend process on startup.
We rely on the Sourcegraph frontend to apply our DB migrations. These live in the /migrations folder. This means:
- The server, bundle manager, and worker wait for the frontend to apply the migration version it cares about before starting.
- We (and more importantly, site admins) only have to care about a single set of DB schema migrations. This is the primary property we benefit from by doing this.
To add a new migration for the tables used by the LSIF processes, create a new migration in the frontend according to the instructions in the migration documentation. Then, update the value of MINIMUM_MIGRATION_VERSION in postgres.ts to be the timestamp from the generated filename.