Function prepare_inference_predicate 

pub fn prepare_inference_predicate<'a>(
    context: InferenceContext<'_>,
    statement: &'a InsertPlan,
    params: &[SQLParam],
) -> Result<Cow<'a, InsertPlan>, SQLError>

Analyze the inference clause in the INSERT target’s scope before uniqueness arbitration, including commands that produce no input rows.