Hello
This bug should be already fixed in stable branch and will be shipped in next minor release. Until the fix is released,
thesimplest workaround is to disable parallel query with SET max_parallel_workers_per_gather = 0 if you're affected by
thebug.
It's a rare timing bug, but some workloads seem to be more prone to it, so unfortunately it went undetected for a long
time.
If you're interested, related discussion and patch was here:
https://www.postgresql.org/message-id/flat/20190207014719.GJ29720%40telsasoft.com
regards, Sergei
