BUG#27211287 - MYSQL SCALABILITY IMPROVEMENT PATCH: OPTIMIZED AWAY EXCESSIVE CONDITION

trx_set_rw_mode() currently has an invalid checking for trx->read_only
which has been already checked by the caller. And from customer's testing,
this can give scalability improvement in OLTP index updates benchmark.

RB: 19234
Reviewed-by: Sunny Bains <[email protected]>

Author: Bin Su

storage/innobase/trx/trx0trx.cc

@@ -3201,6 +3201,7 @@ trx_set_rw_mode(
 	ut_ad(trx->rsegs.m_redo.rseg == 0);
 	ut_ad(!trx->in_rw_trx_list);
 	ut_ad(!trx_is_autocommit_non_locking(trx));
+	ut_ad(!trx->read_only);
 
 	if (srv_force_recovery >= SRV_FORCE_NO_TRX_UNDO) {
 		return;
@@ -3240,11 +3241,9 @@ trx_set_rw_mode(
 	}
 #endif /* UNIV_DEBUG */
 
-	if (!trx->read_only) {
-		UT_LIST_ADD_FIRST(trx_sys->rw_trx_list, trx);
+	UT_LIST_ADD_FIRST(trx_sys->rw_trx_list, trx);
 
-		ut_d(trx->in_rw_trx_list = true);
-	}
+	ut_d(trx->in_rw_trx_list = true);
 
 	mutex_exit(&trx_sys->mutex);
 }