tidb_query_vec_executors: Fixed stack-borrowing undefined-behavior (t…

…ikv#7709)

Signed-off-by: Brian Anderson <[email protected]>

components/tidb_query/src/batch/executors/slow_hash_aggr_executor.rs

@@ -279,7 +279,6 @@ impl<Src: BatchExecutor> AggregationExecutorImpl<Src> for SlowHashAggregationImp
  )?;
  }
 
- let buffer_ptr = (&*self.group_key_buffer).into();
  for logical_row_idx in 0..logical_rows_len {
  let offset_begin = self.group_key_buffer.len();
 
@@ -363,6 +362,7 @@ impl<Src: BatchExecutor> AggregationExecutorImpl<Src> for SlowHashAggregationImp
  }
  }
 
+ let buffer_ptr = (&*self.group_key_buffer).into();
  // Extra column is not included in `GroupKeyRefUnsafe` to avoid being aggr on.
  let group_key_ref_unsafe = GroupKeyRefUnsafe {
  buffer_ptr,