MDEV-17556 Assertion `bitmap_is_set_all(&table->s->all_set)' failed

The assertion failed in handler::ha_reset upon SELECT under
READ UNCOMMITTED from table with index on virtual column.

This was the debug-only failure, though the problem is mush wider:
* MY_BITMAP is a structure containing my_bitmap_map, the latter is a raw
 bitmap.
* read_set, write_set and vcol_set of TABLE are the pointers to MY_BITMAP
* The rest of MY_BITMAPs are stored in TABLE and TABLE_SHARE
* The pointers to the stored MY_BITMAPs, like orig_read_set etc, and
 sometimes all_set and tmp_set, are assigned to the pointers.
* Sometimes tmp_use_all_columns is used to substitute the raw bitmap
 directly with all_set.bitmap
* Sometimes even bitmaps are directly modified, like in
TABLE::update_virtual_field(): bitmap_clear_all(&tmp_set) is called.

The last three bullets in the list, when used together (which is mostly
always) make the program flow cumbersome and impossible to follow,
notwithstanding the errors they cause, like this MDEV-17556, where tmp_set
pointer was assigned to read_set, write_set and vcol_set, then its bitmap
was substituted with all_set.bitmap by dbug_tmp_use_all_columns() call,
and then bitmap_clear_all(&tmp_set) was applied to all this.

To untangle this knot, the rule should be applied:
* Never substitute bitmaps! This patch is about this.
 orig_*, all_set bitmaps are never substituted already.

This patch changes the following function prototypes:
* tmp_use_all_columns, dbug_tmp_use_all_columns
 to accept MY_BITMAP** and to return MY_BITMAP * instead of my_bitmap_map*
* tmp_restore_column_map, dbug_tmp_restore_column_maps to accept
 MY_BITMAP* instead of my_bitmap_map*

These functions now will substitute read_set/write_set/vcol_set directly,
and won't touch underlying bitmaps.

2 files changed, 8 insertions, 9 deletions

diff --git a/storage/rocksdb/ha_rocksdb.cc b/storage/rocksdb/ha_rocksdb.cc
index 5cbe4c162a8..8d2080187ef 100644
--- a/storage/rocksdb/ha_rocksdb.cc
+++ b/storage/rocksdb/ha_rocksdb.cc
@@ -6085,8 +6085,7 @@ ulonglong ha_rocksdb::load_auto_incr_value_from_index() {
     Field *field =
         table->key_info[table->s->next_number_index].key_part[0].field;
     ulonglong max_val = rdb_get_int_col_max_value(field);
-    my_bitmap_map *const old_map =
-        dbug_tmp_use_all_columns(table, table->read_set);
+    MY_BITMAP *const old_map = dbug_tmp_use_all_columns(table, &table->read_set);
     last_val = field->val_int();
     if (last_val != max_val) {
       last_val++;
@@ -6101,7 +6100,7 @@ ulonglong ha_rocksdb::load_auto_incr_value_from_index() {
       }
     }
 #endif
-    dbug_tmp_restore_column_map(table->read_set, old_map);
+    dbug_tmp_restore_column_map(&table->read_set, old_map);
   }
 
   m_keyread_only = save_keyread_only;
@@ -6138,15 +6137,15 @@ void ha_rocksdb::update_auto_incr_val_from_field() {
   field = table->key_info[table->s->next_number_index].key_part[0].field;
   max_val = rdb_get_int_col_max_value(field);
 
-  my_bitmap_map *const old_map =
-      dbug_tmp_use_all_columns(table, table->read_set);
+  MY_BITMAP *const old_map =
+      dbug_tmp_use_all_columns(table, &table->read_set);
   new_val = field->val_int();
   // don't increment if we would wrap around
   if (new_val != max_val) {
     new_val++;
   }
 
-  dbug_tmp_restore_column_map(table->read_set, old_map);
+  dbug_tmp_restore_column_map(&table->read_set, old_map);
 
   // Only update if positive value was set for auto_incr column.
   if (new_val <= max_val) {
diff --git a/storage/rocksdb/rdb_datadic.cc b/storage/rocksdb/rdb_datadic.cc
index fee5d24eb66..31bc40b1df9 100644
--- a/storage/rocksdb/rdb_datadic.cc
+++ b/storage/rocksdb/rdb_datadic.cc
@@ -1488,12 +1488,12 @@ void Rdb_key_def::pack_with_make_sort_key(
   DBUG_ASSERT(*dst != nullptr);
 
   const int max_len = fpi->m_max_image_len;
-  my_bitmap_map *old_map;
+  MY_BITMAP*old_map;
 
   old_map= dbug_tmp_use_all_columns(field->table,
-                                    field->table->read_set);
+                                    &field->table->read_set);
   field->sort_string(*dst, max_len);
-  dbug_tmp_restore_column_map(field->table->read_set, old_map);
+  dbug_tmp_restore_column_map(&field->table->read_set, old_map);
   *dst += max_len;
 }