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Here are my questions:

- does upsert require the id (primary key)? What if it is new data and it still does not have a primary key?
- should the rows in onConflict be unique or can I specify any row?

I hate thinking about upsert and keys...  Here is a quick one I found.
But in general you have to have a unique constraint in order for the insert to "fail" and then do the alternate thing, which can be update...
https://discord.com/channels/839993398554656828/1037065027271790602/1037069569564610561

I meant I want it to insert but the docs say it requires a primary key. So what if it is a new row.

https://github.com/PostgREST/postgrest/issues/1118
More info.   Link is the "workarounds"
Sorry it is late for me and I always struggle with this feature.
https://cdn.discordapp.com/attachments/1111130085697785877/1111136708273111151/image.png

The problem is without a primary key, if there is a conflict, how do I do the update as the primary key is null...

https://postgrest.org/en/stable/references/api/tables_views.html#bulk-insert-with-default-values
This may address that soon, maybe...