Reindexing of foreman database fails with error`could not create unique index "index_fact_names_on_name_and_type"`after the in-place OS upgrade of Satellite 6.11 to RHEL 8

Issue

• After performing the in-place OS upgrade of the Red Hat Satellite 6.11 server from RHEL 7 to 8, the attempt of reindexing all the databases as per the upgrade guide, runs into one or both of the following errors:

  reindexdb: reindexing database "foreman" 
  reindexdb: error: reindexing of database "foreman" failed: ERROR:  could not create unique index "index_fact_names_on_name_and_type"
  DETAIL:  Key (name, type)=(augeasversion, PuppetFactName) is duplicated.   
  

  reindexdb: reindexing database "foreman"
  reindexdb: error: reindexing of database "foreman" failed: ERROR:  could not create unique index "index_fact_names_on_name_and_type"
  DETAIL:  Key (name, type)=(memory::swaptotal, Katello::RhsmFactName) is duplicated.
  

  reindexdb: reindexing database "foreman"
  reindexdb: error: reindexing of database "foreman" failed: ERROR:  could not create unique index "index_fact_names_on_name_and_type"
  DETAIL:  Key (name, type)=(ansible_python::version, ForemanAnsible::FactName) is duplicated.
  

  reindexdb: reindexing database "foreman"
  reindexdb: error: reindexing of database "foreman" failed: ERROR:  could not create unique index "index_fact_names_on_name_and_type"
  DETAIL:  Key (name, type)=(processorcount, DiscoveryFactName) is duplicated.
  

  reindexdb: reindexing database "foreman"
  reindexdb: error: reindexing of database "foreman" failed: ERROR: could not create unique index "katello_available_module_streams_name_stream_context".
  DETAIL: key (name, stream, context)=(pmdk, 1-fileformat-v6, b4937e53) is duplicated.
  

• The problem could also occur during the migration of the whole satellite instance to a new RHEL 8 system.