Fixed some assert crashes related to keyread.

- MDEV-22062 Assertion `!table->file->keyread_enabled()' failed in
  close_thread_table()
- MDEV-22077 table->no_keyread .. failed in join_read_first()
- MDEV-22237 Assertion `!table->file->keyread_enabled()' failed in
  handler::ha_reset on DELETE

mysql-test/main/keyread.result

@@ -4,3 +4,13 @@ select distinct f1 from v1;
 f1
 drop view v1;
 drop table t1;
+CREATE TABLE t1 (a INT NOT NULL, UNIQUE(a)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES (1),(2);
+DELETE FROM t1 ORDER BY a LIMIT 1;
+SELECT * FROM t1;
+a
+2
+DROP TABLE t1;
+CREATE TABLE t1 (a CHAR KEY,b BLOB) ENGINE=InnoDB;
+DELETE FROM t1 ORDER BY a LIMIT 1;
+DROP TABLE t1;

mysql-test/main/keyread.test

@@ -8,3 +8,23 @@ create view v1 as select * from t1 where f2 = 1;
 select distinct f1 from v1;
 drop view v1;
 drop table t1;
+
+#
+# MDEV-22062 Assertion `!table->file->keyread_enabled()' failed in
+# close_thread_table
+#
+
+CREATE TABLE t1 (a INT NOT NULL, UNIQUE(a)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES (1),(2);
+DELETE FROM t1 ORDER BY a LIMIT 1;
+SELECT * FROM t1;
+DROP TABLE t1;
+
+#
+# MDEV-22237 Assertion `!table->file->keyread_enabled()' failed in
+# handler::ha_reset on DELETE
+#
+
+CREATE TABLE t1 (a CHAR KEY,b BLOB) ENGINE=InnoDB;
+DELETE FROM t1 ORDER BY a LIMIT 1;
+DROP TABLE t1;

sql/sql_delete.cc

@@ -379,8 +379,8 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
     tables.table = table;
     tables.alias = table_list->alias;
 
-      if (select_lex->setup_ref_array(thd, order_list->elements) ||
-	  setup_order(thd, select_lex->ref_pointer_array, &tables,
+    if (select_lex->setup_ref_array(thd, order_list->elements) ||
+        setup_order(thd, select_lex->ref_pointer_array, &tables,
                     fields, all_fields, order))
     {
       free_underlaid_joins(thd, thd->lex->first_select_lex());
@@ -547,10 +547,12 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
     else
     {
       ha_rows scanned_limit= query_plan.scanned_rows;
+      table->no_keyread= 1;
       query_plan.index= get_index_for_order(order, table, select, limit,
                                             &scanned_limit,
                                             &query_plan.using_filesort, 
                                             &reverse);
+      table->no_keyread= 0;
       if (!query_plan.using_filesort)
         query_plan.scanned_rows= scanned_limit;
     }

sql/sql_select.cc

@@ -23584,7 +23584,7 @@ check_reverse_order:
          If ref_key used index tree reading only ('Using index' in EXPLAIN),
          and best_key doesn't, then revert the decision.
       */
-      if (table->covering_keys.is_set(best_key))
+      if (table->covering_keys.is_set(best_key) && !table->no_keyread)
         table->file->ha_start_keyread(best_key);
       else
         table->file->ha_end_keyread();
@@ -28568,8 +28568,6 @@ test_if_cheaper_ordering(const JOIN_TAB *tab, ORDER *order, TABLE *table,
   if (new_used_key_parts != NULL)
     *new_used_key_parts= best_key_parts;
   table->file->ha_end_keyread();
-  if (is_best_covering && !table->no_keyread)
-    table->file->ha_start_keyread(best_key);
   DBUG_RETURN(TRUE);
 }
 

sql/sql_update.cc

@@ -614,9 +614,11 @@ int mysql_update(THD *thd,
   else
   {
     ha_rows scanned_limit= query_plan.scanned_rows;
+    table->no_keyread= 1;
     query_plan.index= get_index_for_order(order, table, select, limit,
                                           &scanned_limit, &need_sort,
                                           &reverse);
+    table->no_keyread= 0;
     if (!need_sort)
       query_plan.scanned_rows= scanned_limit;