The INSERT ... ON CONFLICT UPDATE patch has been documented here: https://wiki.postgresql.org/wiki/UPSERT#UPSERT_as_implemented_in_practice https://wiki.postgre

The INSERT ... ON CONFLICT UPDATE patch has been documented here: https://wiki.postgresql.org/wiki/UPSERT#UPSERT_as_implemented_in_practice https://wiki.postgresql.org/wiki/UPSERT#UPSERT_as_implemente... There are some clear benefits possible only thanks to specifying constraint names. Quoted from the link: * The SQL-standard MERGE doesn't provide for choosing an index, so use of a unique index would need to be conditioned on equality quals against indexed columns in order to provide the behavior being discussed for UPSERT. * The ON expression will need to be evaluated to see whether it properly compares to a unique index on the target table. Initially this will need to be done to determine whether the MERGE is allowed at all; later it will determine which sort of plan is allowed. It would be easier to match an index name, provided the index name is known and stable.