I think this will upsert if ANY entry in the table matches this, but not necessarily this id, we can do something like

WHERE NOT EXISTS (select 1 from "${table}" where id = :id AND "${table}"."last_synced_at" > :last_synced_at;)

The integration tests likely did not catch this (if true), given you test for a single entry

Great catch! You're right - I'll add a test to cover this too

I had to do a deep dive into the Postgres docs, but it seems that Postgres actually scopes the WHERE clause in ON CONFLICT DO UPDATE very narrowly.

Specifically:

• The WHERE clause only runs after a conflict is detected (i.e. once a row with matching constraint is found).
• At that point, it only has access to two rows:
  • The conflicting row from the table (via ${table} or alias)
  • The proposed insert row (via excluded)

So even though it looks like ${table}."last_synced_at" could match any row, it actually only refers to the row that caused the conflict.

Source:

• PostgreSQL Docs on INSERT
  “The SET and WHERE clauses in ON CONFLICT DO UPDATE have access to the existing row using the table’s name (or an alias), and to the row proposed for insertion using the special excluded table.”
• This comment on StackOverflow also says the same thing and has a clearer example: https://stackoverflow.com/a/44579804

That said, I find this to be quite non-intuitive (even a bit misleading 😅). I've added a test to verify that this works and reviewed it thoroughly, and I believe it addresses this case. I've added a comment too.

Let me know what you think :)

Sgtm, also tested this locally and it makes sense