Postgres 15 introduces a new syntax to treat nulls as not distinct. This will allow developers to create a unique constraint on nullable fields and have inserts with nulls fail instead of having it allowed based on today's standard.
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https://blog.rustprooflabs.com/2022/07/postgres-15-unique-improvement-with-null
https://www.postgresql.org/message-id/flat/84e5ee1b-387e-9a54-c326-9082674bde78%40enterprisedb.com