From current data at event.rc1_mediawiki_page_content_change we notice that both dt and meta.dt are never NULL:
spark-sql (default)> SELECT count(1)
> FROM rc1_mediawiki_page_content_change
> WHERE dt IS NULL;
count(1)
0
Time taken: 69.411 seconds, Fetched 1 row(s)
spark-sql (default)> SELECT count(1)
> FROM rc1_mediawiki_page_content_change
> WHERE meta.dt IS NULL;
count(1)
0
Time taken: 27.15 seconds, Fetched 1 row(s)But from the page change schema, we notice that meta.dt is not marked as required.
This seems incorrect, as, if there was no meta.dt, the current partitioning strategy of event.rc1_mediawiki_page_content_change would fail.
The ask: make meta.dt required on all schemas that declare it.
Related: Docs suggests it is required: https://wikitech.wikimedia.org/wiki/Event_Platform/Schemas/Guidelines#Required_fields