federated read provider in write table provider (#44)

* federated writer in reader

* simplify

src/duckdb.rs

@@ -231,6 +231,7 @@ impl TableProviderFactory for DuckDBTableProviderFactory {
             None,
         ));
 
+        let read_provider = Arc::new(read_provider.create_federated_table_provider()?);
         Ok(DuckDBTableWriter::create(
             read_provider,
             duckdb,

src/duckdb/write.rs

@@ -29,7 +29,7 @@ use super::to_datafusion_error;
 
 #[derive(Clone)]
 pub struct DuckDBTableWriter {
-    read_provider: Arc<dyn TableProvider>,
+    pub read_provider: Arc<dyn TableProvider>,
     duckdb: Arc<DuckDB>,
     on_conflict: Option<OnConflict>,
 }

src/postgres.rs

@@ -301,6 +301,7 @@ impl TableProviderFactory for PostgresTableProviderFactory {
             Some(Engine::Postgres),
         ));
 
+        let read_provider = Arc::new(read_provider.create_federated_table_provider()?);
         Ok(PostgresTableWriter::create(
             read_provider,
             postgres,

src/sqlite.rs

@@ -255,6 +255,7 @@ impl TableProviderFactory for SqliteTableProviderFactory {
             .context(DanglingReferenceToSqliteSnafu)
             .map_err(to_datafusion_error)?;
 
+        let read_provider = Arc::new(read_provider.create_federated_table_provider()?);
         Ok(SqliteTableWriter::create(
             read_provider,
             sqlite,