# Which Problems Are Solved
Optimize the query that checks for terminated sessions in the access
token verifier. The verifier is used in auth middleware, userinfo and
introspection.
# How the Problems Are Solved
The previous implementation built a query for certain events and then
appended a single `PositionAfter` clause. This caused the postgreSQL
planner to use indexes only for the instance ID, aggregate IDs,
aggregate types and event types. Followed by an expensive sequential
scan for the position. This resulting in internal over-fetching of rows
before the final filter was applied.
Furthermore, the query was searching for events which are not always
applicable. For example, there was always a session ID search and if
there was a user ID, we would also search for a browser fingerprint in
event payload (expensive). Even if those argument string would be empty.
This PR changes:
1. Nest the position query, so that a full `instance_id, aggregate_id,
aggregate_type, event_type, "position"` index can be matched.
2. Redefine the `es_wm` index to include the `position` column.
3. Only search for events for the IDs that actually have a value. Do not
search (noop) if none of session ID, user ID or fingerpint ID are set.
New query plan:
# Additional Changes
- cleanup how we load multi-statement migrations and make that a bit
more reusable.
# Additional Context
- Related to https://github.com/zitadel/zitadel/issues/7639
Even though this is a feature it's released as fix so that we can back port to earlier revisions.
As reported by multiple users startup of ZITADEL after leaded to downtime and worst case rollbacks to the previously deployed version.
The problem starts rising when there are too many events to process after the start of ZITADEL. The root cause are changes on projections (database tables) which must be recomputed. This PR solves this problem by adding a new step to the setup phase which prefills the projections. The step can be enabled by adding the `--init-projections`-flag to `setup`, `start-from-init` and `start-from-setup`. Setting this flag results in potentially longer duration of the setup phase but reduces the risk of the problems mentioned in the paragraph above.
This implementation increases parallel write capabilities of the eventstore.
Please have a look at the technical advisories: [05](https://zitadel.com/docs/support/advisory/a10005) and [06](https://zitadel.com/docs/support/advisory/a10006).
The implementation of eventstore.push is rewritten and stored events are migrated to a new table `eventstore.events2`.
If you are using cockroach: make sure that the database user of ZITADEL has `VIEWACTIVITY` grant. This is used to query events.
