Calculate previous snapshots for deltas automatically.
In this MR we start calculating previous snapshots for deltas automatically with a simple:
SELECT wikiid,page_namespace,page_id,tag,values FROM a.b
WHERE snapshot=(SELECT MAX(DATE(snapshot)) FROM a.b)
ORDER BY page_id
The SELECT MAX(DATE(snapshot)) FROM a.b
is calculated in about ~20 seconds with our current 45 day data retention.
This eliminates the need for the previous_snapshot
parameter, and makes the pipeline resilient to sporadic upstream data failures.
Bug: T330688