[question] howto reuse jqProgram

[Hans van den Bogert]

I'd probably need to reuse the jqprogram, not having invested a lot of time in rust and in particular this library, I'm really not sure how you would do the following.

If you have a need to run the same jq program multiple times it is highly recommended to retain a pre-compiled JqProgram and reuse it.

/update
To clarify, I'd like to reuse the jqProgram across program runs, so I'd probably have to embed the jqProgram somehow or load from disk (?)

[Owen Nelson]

So, the quoted text is referring to using jq_rs::compile() which initializes a jq program which can be run against different inputs over time. This won't really help you across different program runs - you'll always have to pay the cost of compiling the jq program at least once per run.

I should add an example of this type of usage.

In the meantime, I hope this helps explain how you'd use it...

fn main() {
  // compile the jq program once
  let mut prog = jq_rs::compile(".name").unwrap();
  // run the program over some json...
  assert_eq!("\"alice\"", prog.run(r#"{"name": "alice"}"#).unwrap());
  // run the program over some other json...
  assert_eq!("\"bob\"", prog.run(r#"{"name": "bob"}"#).unwrap());
}

The reason reusing an already compiled jq program is attractive is because this compilation step is quite slow - or at least it's slow at the v1.6 tag for jq. Apparently there was a big slowdown between v1.5 and v1.6, and some steps were later taken to mitigate this in jq master. We'll reap the benefit here whenever they decide to tag v1.7 (but I don't have a sense of when that might be).

[Hans van den Bogert]

Thank you for your elaborate answer(s). Just to be really certain, there is no way to serialize (for lack of a better word) the jqProgram and reload it in consecutive invocations of program runs, i.e., libjq does not provide this functionality?

[Owen Nelson]

Just to be really certain, there is no way to serialize (for lack of a better word) the jqProgram and reload it in consecutive invocations of program runs, i.e., libjq does not provide this functionality?

That's correct, as far as I know.