Comment by dgacmu | Hacker News Reader

Comment by dgacmu | Hacker News Reader

This kind of sells the reason not to wrap things behind an object interface, doesn't it?

    for fan in c.query("SELECT * FROM Win32_Fan"):
        if fan.wmi_property("ActiveCooling").value is True:
            print(f"Fan `{fan.wmi_property('Name').value}` is running at {fan.wmi_property('DesiredSpeed').value} RPM")

vs "SELECT Name, DesiredSpeed from Win32_Fan where ActiveCooling"

Obviously, this doesn't matter when you have 5 fans, but in general, you want to push your restrictions as deeply into the query as possible from an optimization standpoint.

In WMI, the fields are lazy loaded when you do a `*` query, but the real crate [does use the same Serde reflection tricks](https://github.com/ohadravid/wmi-rs/blob/main/src/query.rs#L...) to create the correct field list when you query a struct which improves perf a lot!

> Obviously, this doesn't matter when you have 5 fans, but in general, you want to push your restrictions as deeply into the query as possible from an optimization standpoint.

Depends where the database lives. If it's an in-process SQLite DB instance, there's no difference & doing this in code is easier to understand than more complicated SQL queries (of course not necessarily in this case but in general). But in all other cases you are correct about efficiency in general (although again other effects can dominate & make it irrelevant).

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