MDEV-28552 Assertion `inited==RND' failed in handler::ha_rnd_end

We cannot permanently change bits in read_partitions in the middle of
processing because ha_rnd_init()/ha_rnd_end() depends on that.

mysql-test/suite/versioning/r/partition.result

@@ -1133,5 +1133,17 @@ select count(*) from t1 partition (p1);
 count(*)
 100
 drop table t1;
+#
+# MDEV-28552 Assertion `inited==RND' failed in handler::ha_rnd_end
+#
+create table tcount (c int unsigned);
+insert into tcount values (0);
+create table t (f int) with system versioning
+partition by system_time limit 1000
+(partition p1 history, partition pn current);
+insert into t values (1),(2);
+create trigger tr before insert on t for each row update tcount set c = c + 1;
+insert into t select * from t;
+drop table tcount, t;
 # End of 10.3 tests
 set global innodb_stats_persistent= @save_persistent;

mysql-test/suite/versioning/t/partition.test

@@ -1080,6 +1080,24 @@ replace t1 select * from t1;
 select count(*) from t1 partition (p0);
 select count(*) from t1 partition (p1);
 drop table t1;
+
+--echo #
+--echo # MDEV-28552 Assertion `inited==RND' failed in handler::ha_rnd_end
+--echo #
+create table tcount (c int unsigned);
+insert into tcount values (0);
+
+create table t (f int) with system versioning
+partition by system_time limit 1000
+(partition p1 history, partition pn current);
+insert into t values (1),(2);
+create trigger tr before insert on t for each row update tcount set c = c + 1;
+
+insert into t select * from t;
+
+# cleanup
+drop table tcount, t;
+
 --echo # End of 10.3 tests
 
 set global innodb_stats_persistent= @save_persistent;

sql/ha_partition.h

@@ -1608,7 +1608,6 @@ class ha_partition :public handler
     for (; part_id < part_id_end; ++part_id)
     {
       handler *file= m_file[part_id];
-      DBUG_ASSERT(bitmap_is_set(&(m_part_info->read_partitions), part_id));
       file->info(HA_STATUS_VARIABLE | HA_STATUS_NO_LOCK | HA_STATUS_OPEN);
       part_recs+= file->stats.records;
     }

sql/partition_info.cc

@@ -904,8 +904,6 @@ void partition_info::vers_check_limit(THD *thd)
   uint32 part_id= vers_info->hist_part->id * sub_factor;
   const uint32 part_id_end= part_id + sub_factor;
   DBUG_ASSERT(part_id_end <= num_parts * sub_factor);
-  for (; part_id < part_id_end; ++part_id)
-    bitmap_set_bit(&read_partitions, part_id);
 
   ha_partition *hp= (ha_partition*)(table->file);
   ha_rows hist_rows= hp->part_records(vers_info->hist_part);