[doc] clearer doc about why sql() is async

Author: rdettai

ballista/rust/client/src/context.rs

@@ -238,7 +238,8 @@ impl BallistaContext {
 
     /// Create a DataFrame from a SQL statement.
     ///
-    /// Async because CreateExternalTable might require to resolve the schema
+    /// This method is `async` because queries of type `CREATE EXTERNAL TABLE`
+    /// might require the schema to be infered.
     pub async fn sql(&self, sql: &str) -> Result<Arc<dyn DataFrame>> {
         let mut ctx = {
             let state = self.state.lock().unwrap();

ballista/rust/core/proto/ballista.proto

@@ -20,8 +20,6 @@ syntax = "proto3";
 
 package ballista.protobuf;
 
-import "google/protobuf/timestamp.proto";
-
 option java_multiple_files = true;
 option java_package = "org.ballistacompute.protobuf";
 option java_outer_classname = "BallistaProto";

datafusion/src/execution/context.rs

@@ -182,7 +182,8 @@ impl ExecutionContext {
 
     /// Creates a dataframe that will execute a SQL query.
     ///
-    /// async because CreateExternalTable queries might need schema inference
+    /// This method is `async` because queries of type `CREATE EXTERNAL TABLE`
+    /// might require the schema to be infered.
     pub async fn sql(&mut self, sql: &str) -> Result<Arc<dyn DataFrame>> {
         let plan = self.create_logical_plan(sql)?;
         match plan {