feat: use optimised logical plan for schema

Author: sunng87

Cargo.lock

@@ -346,7 +346,10 @@ pub enum Error {
     },
 
     #[snafu(display("Failed to describe schema for given statement, source: {}", source))]
-    DescribeStatement { source: query::error::Error },
+    DescribeStatement {
+        #[snafu(backtrace)]
+        source: query::error::Error,
+    },
 }
 
 pub type Result<T> = std::result::Result<T, Error>;

src/frontend/src/error.rs

@@ -104,7 +104,12 @@ impl QueryEngine for DatafusionQueryEngine {
     }
 
     fn describe(&self, stmt: QueryStatement, query_ctx: QueryContextRef) -> Result<Schema> {
-        self.statement_to_plan(stmt, query_ctx)?.schema()
+        // TODO(sunng87): consider cache optmised logical plan between describe
+        // and execute
+        let plan = self.statement_to_plan(stmt, query_ctx)?;
+        let mut ctx = QueryEngineContext::new(self.state.clone());
+        let optimised_plan = self.optimize_logical_plan(&mut ctx, &plan)?;
+        optimised_plan.schema()
     }
 
     async fn execute(&self, plan: &LogicalPlan) -> Result<Output> {