This note is in Hasura.RQL.DDL.Metadata. It is referenced at:
There was an issue (https://github.com/hasura/graphql-engine/issues/5461) fixed (via https://github.com/hasura/graphql-engine/pull/6137) related to event triggers while replacing metadata in the catalog prior to metadata separation. The metadata separation solves the issue naturally, since the ‘hdb_catalog.event_triggers’ table is no more in use and new/updated event triggers are processed in building schema cache. But we need to drop the database trigger and archive events for dropped event triggers. This is handled explicitly in @’runReplaceMetadata’ function.