# Which Problems Are Solved
For truly event-based notification handler, we need to be able to filter
out events of aggregates which are already handled. For example when an
event like `notify.success` or `notify.failed` was created on an
aggregate, we no longer require events from that aggregate ID.
# How the Problems Are Solved
Extend the query builder to use a `NOT IN` clause which excludes
aggregate IDs when they have certain events for a certain aggregate
type. For optimization and proper index usages, certain filters are
inherited from the parent query, such as:
- Instance ID
- Instance IDs
- Position offset
This is a prettified query as used by the unit tests:
```sql
SELECT created_at, event_type, "sequence", "position", payload, creator, "owner", instance_id, aggregate_type, aggregate_id, revision
FROM eventstore.events2
WHERE instance_id = $1
AND aggregate_type = $2
AND event_type = $3
AND "position" > $4
AND aggregate_id NOT IN (
SELECT aggregate_id
FROM eventstore.events2
WHERE aggregate_type = $5
AND event_type = ANY($6)
AND instance_id = $7
AND "position" > $8
)
ORDER BY "position" DESC, in_tx_order DESC
LIMIT $9
```
I used this query to run it against the `oidc_session` aggregate looking
for added events, excluding aggregates where a token was revoked,
against a recent position. It fully used index scans:
<details>
```json
[
{
"Plan": {
"Node Type": "Index Scan",
"Parallel Aware": false,
"Async Capable": false,
"Scan Direction": "Forward",
"Index Name": "es_projection",
"Relation Name": "events2",
"Alias": "events2",
"Actual Rows": 2,
"Actual Loops": 1,
"Index Cond": "((instance_id = '286399006995644420'::text) AND (aggregate_type = 'oidc_session'::text) AND (event_type = 'oidc_session.added'::text) AND (\"position\" > 1731582100.784168))",
"Rows Removed by Index Recheck": 0,
"Filter": "(NOT (hashed SubPlan 1))",
"Rows Removed by Filter": 1,
"Plans": [
{
"Node Type": "Index Scan",
"Parent Relationship": "SubPlan",
"Subplan Name": "SubPlan 1",
"Parallel Aware": false,
"Async Capable": false,
"Scan Direction": "Forward",
"Index Name": "es_projection",
"Relation Name": "events2",
"Alias": "events2_1",
"Actual Rows": 1,
"Actual Loops": 1,
"Index Cond": "((instance_id = '286399006995644420'::text) AND (aggregate_type = 'oidc_session'::text) AND (event_type = 'oidc_session.access_token.revoked'::text) AND (\"position\" > 1731582100.784168))",
"Rows Removed by Index Recheck": 0
}
]
},
"Triggers": [
]
}
]
```
</details>
# Additional Changes
- None
# Additional Context
- Related to https://github.com/zitadel/zitadel/issues/8931
---------
Co-authored-by: adlerhurst <silvan.reusser@gmail.com>
# Which Problems Are Solved
Float64 which was used for the event.Position field is [not precise in
go and gets rounded](https://github.com/golang/go/issues/47300). This
can lead to unprecies position tracking of events and therefore
projections especially on cockcoachdb as the position used there is a
big number.
example of a unprecies position:
exact: 1725257931223002628
float64: 1725257931223002624.000000
# How the Problems Are Solved
The float64 was replaced by
[github.com/jackc/pgx-shopspring-decimal](https://github.com/jackc/pgx-shopspring-decimal).
# Additional Changes
Correct behaviour of makefile for load tests.
Rename `latestSequence`-queries to `latestPosition`
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.
