[fix #8904] Improved output of datafuson-cli with empty results

datafusion-cli/src/exec.rs

@@ -239,6 +239,7 @@ async fn exec_and_print(
 
         let df = ctx.execute_logical_plan(plan).await?;
         let physical_plan = df.create_physical_plan().await?;
+        let schema = physical_plan.schema();
 
         if is_plan_streaming(&physical_plan)? {
             let stream = execute_stream(physical_plan, task_ctx.clone())?;
@@ -252,7 +253,7 @@ async fn exec_and_print(
                 print_options.format = PrintFormat::Table;
             }
             let results = collect(physical_plan, task_ctx.clone()).await?;
-            print_options.print_batches(&results, now)?;
+            print_options.print_batches_with_empty_result(&results, schema, now)?;
         }
     }
 

datafusion-cli/src/print_options.rs

@@ -23,7 +23,8 @@ use std::time::Instant;
 
 use crate::print_format::PrintFormat;
 
-use arrow::record_batch::RecordBatch;
+use arrow::datatypes::SchemaRef;
+use arrow::record_batch::{RecordBatch, RecordBatchOptions};
 use datafusion::common::DataFusionError;
 use datafusion::error::Result;
 use datafusion::physical_plan::RecordBatchStream;
@@ -94,6 +95,23 @@ fn get_timing_info_str(
 }
 
 impl PrintOptions {
+    pub fn print_batches_with_empty_result(
+        &self,
+        batches: &[RecordBatch],
+        schema: SchemaRef,
+        query_start_time: Instant,
+    ) -> Result<()> {
+        if batches.len() == 0 {
+            let option = RecordBatchOptions::new().with_match_field_names(false);
+
+            return self.print_batches(
+                &[RecordBatch::try_new_with_options(schema, vec![], &option)?],
+                query_start_time,
+            );
+        };
+        return self.print_batches(batches, query_start_time);
+    }
+
     /// Print the batches to stdout using the specified format
     pub fn print_batches(
         &self,

datafusion/core/tests/user_defined/user_defined_scalar_functions.rs

@@ -209,8 +209,10 @@ async fn scalar_udf_zero_params() -> Result<()> {
 
     let result = plan_and_collect(&ctx, "select get_100() from t where a=999").await?;
     let expected = [
-        "++", //
-        "++",
+        "+-----------+",
+        "| get_100() |",
+        "+-----------+",
+        "+-----------+",
     ];
     assert_batches_eq!(expected, &result);
     Ok(())