While renaming a 100+ page .djvu files I received the following errors:
Wystąpił błąd podczas wykonywania zapytania do bazy danych. Może to wskazywać na błąd w oprogramowaniu. [W7dvpgrAADsAAExNO0QAAACG] 2018-10-05 14:06:41: Krytyczny wyjątek typu "Wikimedia\Rdbms\DBExpectedError"
(while moving File:PL Karol May - Grobowiec Rodrigandów.djvu -> File:Karol May - Grobowiec Rodrigandów.djvu)
Wystąpił błąd podczas wykonywania zapytania do bazy danych. Może to wskazywać na błąd w oprogramowaniu. [W7eQGgrAIFAAALDOcM8AAAAD] 2018-10-05 16:25:06: Krytyczny wyjątek typu "Wikimedia\Rdbms\DBExpectedError"
(while moving File:PL Karol May - Benito Juarez.djvu -> File:Karol May - Benito Juarez.djvu)
The circumstances were the same in both cases: the move took a lot of time and after about a minute since it has been initiated, I checked in another tab whether the move has completed already. The check result was: there was already a redirect under the source name and a message that the file does not exist under the target name. A while after the check, the error message appeared in the file move window.
I did not observe a problem with the moved file after receiving the error. So reporting here just for tracking.
It seems to me that the errors are related to the access attempt to a file while its move is in progress.