In https://gerrit.wikimedia.org/r/#/c/mediawiki/core/+/459885/ streaming mode in WikiExport was removed. Stub dumps used to write 2000 to 4000 revisions per second; now they write 1000 revisions in 2 to 3 minutes. On ruwiktionary, for example, the job is so slow that no new data has been written to the gzipped stubs output files since 5 am Oct 21 (it's 7 am Oct 22 now).
The new query uses a temp table and filesort and much too small a batch size. We need to fix this up.