Update ChangeLog.md and add a test

Author: kubo

ChangeLog.md

@@ -11,6 +11,13 @@ Non-breaking Changes:
 
 * `DbError::new()` uses generics, which supports old types.
 
+Internal Changes:
+
+* Improve performance of iterator for [`ResultSet<T>`][`ResultSet`] where T is [`Row`]
+  by sharing an internal fetch array buffer. Before this change, one row in the buffer
+  is copied to `Row` for each iteration. After this, new fetch array buffer is allocated
+  when more rows must be fetched into a buffer but the buffer is referenced by `Row`s.
+
 ## 0.6.0 (2024-05-20)
 
 Breaking changes:

src/statement.rs

@@ -1485,4 +1485,25 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn fetch_rows_to_vec() -> Result<()> {
+        let conn = test_util::connect()?;
+        // The fetch array size must be less than the number of rows in TestStrings
+        // in order to make situation that a new fetch array buffer must allocated
+        // in Stmt::fetch_rows().
+        let mut stmt = conn
+            .statement("select IntCol from TestStrings order by IntCol")
+            .fetch_array_size(3)
+            .build()?;
+        let mut rows = Vec::new();
+        for row_result in stmt.query(&[])? {
+            rows.push(row_result?);
+        }
+        for (index, row) in rows.iter().enumerate() {
+            let int_col: usize = row.get(0)?;
+            assert_eq!(int_col, index + 1);
+        }
+        Ok(())
+    }
 }