Disable prefetch and adaptive hash index for tables with rows over 1024

bytes in InnoDB's SQL parser.

row/row0sel.c

@@ -45,6 +45,9 @@ to que_run_threads: this is to allow canceling runaway queries */
 
 #define SEL_COST_LIMIT	100
 
+/* The lower limit for what we consider a "big" row */
+#define BIG_ROW_SIZE	1024
+
 /* Flags for search shortcut */
 #define SEL_FOUND	0
 #define	SEL_EXHAUSTED	1
@@ -1240,7 +1243,8 @@ row_sel(
 	mtr_start(&mtr);
 
 	if (consistent_read && plan->unique_search && !plan->pcur_is_open
-						&& !plan->must_get_clust) {
+			&& !plan->must_get_clust
+			&& (plan->table->max_row_size < BIG_ROW_SIZE)) {
 		if (!search_latch_locked) {
 			rw_lock_s_lock(&btr_search_latch);
 
@@ -1628,7 +1632,8 @@ row_sel(
 	}
 
 	if ((plan->n_rows_fetched <= SEL_PREFETCH_LIMIT)
-				|| plan->unique_search || plan->no_prefetch) {
+		|| plan->unique_search || plan->no_prefetch
+		|| (plan->table->max_row_size >= BIG_ROW_SIZE)) {
 
 		/* No prefetch in operation: go to the next table */