on 1.28.0-wmf.17 on testwikidatawiki and wikidatawiki at least:
A fair share of
Wikibase\Client\Usage\Sql\EntityUsageTable::addUsages: Implicit transaction already active
(from DatabaseBase::query (Wikibase\Client\Usage\Sql\EntityUsageTable::queryUsages)).
Wikibase\Client\Usage\Sql\EntityUsageTable::addUsages: Explicit commit of implicit transaction.And at least one related to removeUsage
Wikibase\Client\Usage\Sql\EntityUsageTable::removeUsages: Implicit transaction already active (from DatabaseBase::query (User::idFromName)).
Simiar to T144433: Wikibase\SqlIdGenerator::generateNewId: Implicit transaction expected (DBO_TRX set).