Why the PhysicalPlanner is an async trait ?

[mingmwang]

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I have a question for the PhysicalPlanner, looks like in current DataFusion implement, the logical plan creation and optimization is the normal sync functions, but PhysicalPlanner is async, why ?

#[async_trait]
pub trait PhysicalPlanner: Send + Sync {
    /// Create a physical plan from a logical plan
    async fn create_physical_plan(
        &self,
        logical_plan: &LogicalPlan,
        session_state: &SessionState,
    ) -> Result<Arc<dyn ExecutionPlan>>;
}

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[yjshen]

The scan in TableProvider which creates a physical scan plan from a logical table scan is async. It needs to list partitions and gather statistics that are async.

[mingmwang]

Thanks a lot for the explanation.