+ /* Optimize the trivial case where we're not going to do
+ anything with the data, by not reading the data at all. */
+ if (case_func == NULL && end_func == NULL
+ && case_source_is_class (vfm_source, &storage_source_class)
+ && vfm_sink == NULL
+ && (temporary_trns_chain == NULL
+ || trns_chain_is_empty (temporary_trns_chain))
+ && trns_chain_is_empty (permanent_trns_chain))
+ {
+ n_lag = 0;
+ expr_free (process_if_expr);
+ process_if_expr = NULL;
+ dict_set_case_limit (default_dict, 0);
+ dict_clear_vectors (default_dict);
+ return true;
+ }
+
+ open_active_file ();
+
+ wc_data.case_func = case_func;