Zero-copy conversion from SchemaRef to DfSchema (#10298)

Author: tustvold

datafusion/common/src/dfschema.rs

@@ -810,9 +810,16 @@ impl From<&DFSchema> for Schema {
 impl TryFrom<Schema> for DFSchema {
     type Error = DataFusionError;
     fn try_from(schema: Schema) -> Result<Self, Self::Error> {
+        Self::try_from(Arc::new(schema))
+    }
+}
+
+impl TryFrom<SchemaRef> for DFSchema {
+    type Error = DataFusionError;
+    fn try_from(schema: SchemaRef) -> Result<Self, Self::Error> {
         let field_count = schema.fields.len();
         let dfschema = Self {
-            inner: schema.into(),
+            inner: schema,
             field_qualifiers: vec![None; field_count],
             functional_dependencies: FunctionalDependencies::empty(),
         };
@@ -856,12 +863,7 @@ impl ToDFSchema for Schema {
 
 impl ToDFSchema for SchemaRef {
     fn to_dfschema(self) -> Result<DFSchema> {
-        // Attempt to use the Schema directly if there are no other
-        // references, otherwise clone
-        match Self::try_unwrap(self) {
-            Ok(schema) => DFSchema::try_from(schema),
-            Err(schemaref) => DFSchema::try_from(schemaref.as_ref().clone()),
-        }
+        DFSchema::try_from(self)
     }
 }