yes i'm very sure. from what i observed, it has something to do with the concurrent query planing. if i disconnect other connections, the plan is very quick.
Used partition schema looks very simple and straightforward, and should have no issues with 80 partitions. Are you sure that you have only 80 partitions but not (lets say) 800?
Are every other partition of the article table use the same general idea of partition check (cid=something)?
"People problems are solved with people. If people cannot solve the problem, try technology. People will then wish they'd listened at the first stage."