MDEV-21936 Assertion !btr_search_own... in btr_search_drop_page_hash_index

This is a regression due to the cleanup
commit 12f804ac.

row_sel_open_pcur(): Remove the unnecessary parameter.
It suffices for us to acquire the adaptive hash index latch
only when btr_search_guess_on_hash() is called by
btr_cur_search_to_nth_level_func(), in
btr_pcur_open_with_no_init().

This code seems to be a relic from the times when there was
only one btr_search_latch, which was held in shared mode
for longer periods of time. Another relic of that era was
removed in commit e5980bf1.
This clean-up was missed when the btr_search_latch was split in
mysql/mysql-server/commit@ab17ab91ce18a47bb6c5c49e4dc0505ad488a448
(MySQL 5.7.8).

storage/innobase/row/row0sel.cc

@@ -1288,10 +1288,6 @@ void
 row_sel_open_pcur(
 /*==============*/
 	plan_t*		plan,	/*!< in: table plan */
-#ifdef BTR_CUR_HASH_ADAPT
-	rw_lock_t*	ahi_latch,
-				/*!< in: the adaptive hash index latch */
-#endif /* BTR_CUR_HASH_ADAPT */
 	mtr_t*		mtr)	/*!< in/out: mini-transaction */
 {
 	dict_index_t*	index;
@@ -1335,7 +1331,7 @@ row_sel_open_pcur(
 
 		btr_pcur_open_with_no_init(index, plan->tuple, plan->mode,
 					   BTR_SEARCH_LEAF, &plan->pcur,
-					   ahi_latch, mtr);
+					   NULL, mtr);
 	} else {
 		/* Open the cursor to the start or the end of the index
 		(FALSE: no init) */
@@ -1480,16 +1476,12 @@ row_sel_try_search_shortcut(
 	ut_ad(plan->unique_search);
 	ut_ad(!plan->must_get_clust);
 
-	rw_lock_t* ahi_latch = btr_get_search_latch(index);
-	rw_lock_s_lock(ahi_latch);
-
-	row_sel_open_pcur(plan, ahi_latch, mtr);
+	row_sel_open_pcur(plan, mtr);
 
 	const rec_t* rec = btr_pcur_get_rec(&(plan->pcur));
 
 	if (!page_rec_is_user_rec(rec) || rec_is_metadata(rec, index)) {
 retry:
-		rw_lock_s_unlock(ahi_latch);
 		return(SEL_RETRY);
 	}
 
@@ -1501,7 +1493,6 @@ row_sel_try_search_shortcut(
 
 	if (btr_pcur_get_up_match(&(plan->pcur)) < plan->n_exact_match) {
 exhausted:
-		rw_lock_s_unlock(ahi_latch);
 		return(SEL_EXHAUSTED);
 	}
 
@@ -1547,7 +1538,6 @@ row_sel_try_search_shortcut(
 	ut_ad(plan->pcur.latch_mode == BTR_SEARCH_LEAF);
 
 	plan->n_rows_fetched++;
-	rw_lock_s_unlock(ahi_latch);
 
 	if (UNIV_LIKELY_NULL(heap)) {
 		mem_heap_free(heap);
@@ -1669,11 +1659,7 @@ row_sel(
 	if (!plan->pcur_is_open) {
 		/* Evaluate the expressions to build the search tuple and
 		open the cursor */
-		row_sel_open_pcur(plan,
-#ifdef BTR_CUR_HASH_ADAPT
-				  NULL,
-#endif /* BTR_CUR_HASH_ADAPT */
-				  &mtr);
+		row_sel_open_pcur(plan, &mtr);
 
 		cursor_just_opened = TRUE;