more concise docs

datafusion/expr/src/registry.rs

@@ -151,24 +151,17 @@ pub trait SerializerRegistry: Debug + Send + Sync {
         )
     }
 
-    /// Binary representation for custom tables, to be converted to substrait extension tables.
-    /// Should only return success for table implementations that cannot be found by name
-    /// in the destination execution context, such as UDTFs or manually registered table providers.
+    /// Serialized table definition for UDTFs or manually registered table providers that can't be
+    /// marshaled by reference. Should return some benign error for regular tables that can be
+    /// found/restored by name in the destination execution context.
     fn serialize_custom_table(&self, _table: &dyn TableSource) -> Result<Vec<u8>> {
         not_impl_err!("No custom table support")
     }
 
     /// Deserialize the custom table with the given name.
-    /// The name may not be useful as a discriminator if multiple UDTF/TableProvider
-    /// implementations are expected. This is particularly true for UDTFs in DataFusion,
-    /// which are always registered under the same name: `tmp_table`, so one should
-    /// use the binary payload to distinguish between multiple potential table types.
-    /// A potential future improvement would be to return a (name, bytes) tuple from
-    /// [SerializerRegistry::serialize_custom_table] to allow the implementors to assign
-    /// different names to different table provider implementations (e.g. in the case of proto,
-    /// by using the actual protobuf `type_url`).
-    /// But this would mean the table names in the restored plan may no longer match
-    /// the original ones.
+    /// Note: more often than not, the name can't be used as a discriminator if multiple different
+    /// `TableSource` and/or `TableProvider` implementations are expected (this is particularly true
+    /// for UDTFs in DataFusion, which are always registered under the same name: `tmp_table`).
     fn deserialize_custom_table(
         &self,
         name: &str,

datafusion/substrait/src/logical_plan/consumer.rs

@@ -1001,13 +1001,11 @@ pub async fn from_substrait_rel(
                                 &ext_detail.type_url,
                                 &ext_detail.value,
                             )?;
-                        let table_name = if let Some((_, name)) =
-                            ext_detail.type_url.rsplit_once('/')
-                        {
-                            name
-                        } else {
-                            &ext_detail.type_url
-                        };
+                        let table_name = ext_detail
+                            .type_url
+                            .rsplit_once('/')
+                            .map(|(_, name)| name)
+                            .unwrap_or(&ext_detail.type_url);
                         let plan = LogicalPlan::TableScan(TableScan::try_new(
                             table_name,
                             source,