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> Yeah, TIMESTAMPTZ expressions don’t index nicely because they’re nondeterministic

Could you expand on why it's not deterministic? I thought timestamptz was 8-byte microseconds since the epoch. Is the problem that the timestamptz uses the server timezone?

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Yeah, you've got the right idea. Specifically, functions that operate on TIMESTAMPTZ aren't typically marked as IMMUTABLE (because their output implicitly depends on the connection-level time zone setting), and that IMMUTABLE flag is required for functions used in indexed expressions.

https://www.postgresql.org/docs/current/xfunc-volatility.htm...

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