I think those are used while migration from postgres 10 to 12 as I’ve seen these in almost every user whose indexes have had issues. E.g.
https://meta.discourse.org/t/postgresql-12-update/151236/208?u=itsbhanusharma
https://meta.discourse.org/t/postgresql-12-update/151236/237?u=itsbhanusharma
EDIT: comes from postgres itself
The recommended recovery method in such cases is to drop the invalid index and try again to perform
REINDEX CONCURRENTLY
. The concurrent index created during the processing has a name ending in the suffixccnew
, orccold
if it is an old index definition which we failed to drop. Invalid indexes can be dropped usingDROP INDEX
, including invalid toast indexes.