return empty dataframe on create table, remove a duplicate optimize c…

…all (#3361)

update docs

datafusion/core/src/execution/context.rs

@@ -269,35 +269,33 @@ impl SessionContext {
                     (true, false, Ok(_)) => self.return_empty_dataframe(),
                     (false, true, Ok(_)) => {
                         self.deregister_table(name.as_str())?;
-                        let plan = self.optimize(&input)?;
                         let physical =
-                            Arc::new(DataFrame::new(self.state.clone(), &plan));
+                            Arc::new(DataFrame::new(self.state.clone(), &input));
 
                         let batches: Vec<_> = physical.collect_partitioned().await?;
                         let table = Arc::new(MemTable::try_new(
-                            Arc::new(plan.schema().as_ref().into()),
+                            Arc::new(input.schema().as_ref().into()),
                             batches,
                         )?);
 
                         self.register_table(name.as_str(), table)?;
-                        Ok(Arc::new(DataFrame::new(self.state.clone(), &plan)))
+                        self.return_empty_dataframe()
                     }
                     (true, true, Ok(_)) => Err(DataFusionError::Internal(
                         "'IF NOT EXISTS' cannot coexist with 'REPLACE'".to_string(),
                     )),
                     (_, _, Err(_)) => {
-                        let plan = self.optimize(&input)?;
                         let physical =
-                            Arc::new(DataFrame::new(self.state.clone(), &plan));
+                            Arc::new(DataFrame::new(self.state.clone(), &input));
 
                         let batches: Vec<_> = physical.collect_partitioned().await?;
                         let table = Arc::new(MemTable::try_new(
-                            Arc::new(plan.schema().as_ref().into()),
+                            Arc::new(input.schema().as_ref().into()),
                             batches,
                         )?);
 
                         self.register_table(name.as_str(), table)?;
-                        Ok(Arc::new(DataFrame::new(self.state.clone(), &plan)))
+                        self.return_empty_dataframe()
                     }
                     (false, false, Ok(_)) => Err(DataFusionError::Execution(format!(
                         "Table '{:?}' already exists",

datafusion/core/tests/sql/create_drop.rs

@@ -57,12 +57,14 @@ async fn create_or_replace_table_as() -> Result<()> {
         SessionContext::with_config(SessionConfig::new().with_information_schema(true));
 
     // Create table
-    ctx.sql("CREATE TABLE y AS VALUES (1,2),(3,4)")
+    let result = ctx
+        .sql("CREATE TABLE y AS VALUES (1,2),(3,4)")
         .await
         .unwrap()
         .collect()
         .await
         .unwrap();
+    assert!(result.is_empty());
 
     // Replace table
     ctx.sql("CREATE OR REPLACE TABLE y AS VALUES (5,6)")

docs/source/user-guide/sql/ddl.md

@@ -78,16 +78,16 @@ PARTITIONED BY (year, month)
 LOCATION '/mnt/nyctaxi';
 ```
 
-## CREATE MEMORY TABLE
+## CREATE TABLE
 
-Memory table can be created with query.
+An in-memory table can be created with a query or values list.
 
-```
-CREATE TABLE TABLE_NAME AS [SELECT | VALUES LIST]
-```
+<pre>
+CREATE [OR REPLACE] TABLE [IF NOT EXISTS] <b><i>table_name</i></b> AS [SELECT | VALUES LIST];
+</pre>
 
 ```sql
-CREATE TABLE valuetable AS VALUES(1,'HELLO'),(12,'DATAFUSION');
+CREATE TABLE valuetable IF NOT EXISTS AS VALUES(1,'HELLO'),(12,'DATAFUSION');
 
 CREATE TABLE memtable as select * from valuetable;
 ```