refactor(odbc): change OdbcBatch columns to use Arc for improved memory efficiency

This commit updates the OdbcBatch structure to store columns as an Arc array, enhancing memory management and reducing cloning overhead. The change is reflected in both the OdbcBatch definition and its instantiation within the ODBC bridge.

Author: lovasoa

sqlx-core/src/odbc/connection/odbc_bridge.rs

@@ -246,6 +246,9 @@ where
 
     let mut receiver_open = true;
 
+    let columns: Vec<OdbcColumn> = bindings.iter().map(|b| b.column.clone()).collect();
+    let col_arc: Arc<[OdbcColumn]> = Arc::from(columns);
+
     while let Some(batch) = row_set_cursor.fetch()? {
         // Create ColumnData instances that can be shared across rows
         let column_data: Vec<_> = bindings
@@ -257,7 +260,7 @@ where
             .collect();
 
         let odbc_batch = Arc::new(OdbcBatch {
-            columns: bindings.iter().map(|b| b.column.clone()).collect(),
+            columns: Arc::clone(&col_arc),
             column_data,
         });
 

sqlx-core/src/odbc/row.rs

@@ -7,7 +7,7 @@ use std::sync::Arc;
 
 #[derive(Debug, Clone)]
 pub struct OdbcBatch {
-    pub(crate) columns: Vec<OdbcColumn>,
+    pub(crate) columns: Arc<[OdbcColumn]>,
     pub(crate) column_data: Vec<Arc<crate::odbc::ColumnData>>,
 }