MDEV-24176 Preparations

1. moved fix_vcol_exprs() call to open_table()

mysql_alter_table() doesn't do lock_tables() so it cannot win from
fix_vcol_exprs() from there. Tests affected: main.default_session

2. Vanilla cleanups and comments.

sql/field.h

@@ -616,6 +616,10 @@ class Virtual_column_info: public Sql_alloc
   {
     in_partitioning_expr= TRUE;
   }
+  bool fix_expr(THD *thd);
+  bool fix_session_expr(THD *thd);
+  bool fix_session_expr_for_read(THD *thd, Field *field);
+  bool fix_and_check_expr(THD *thd, TABLE *table);
   inline bool is_equal(const Virtual_column_info* vcol) const;
   inline void print(String*);
 };

sql/item.cc

@@ -6376,8 +6376,9 @@ bool Item_field::fix_fields(THD *thd, Item **reference)
   }
 #endif
   fixed= 1;
-  if (field->vcol_info)
-    fix_session_vcol_expr_for_read(thd, field, field->vcol_info);
+  if (field->vcol_info &&
+      field->vcol_info->fix_session_expr_for_read(thd, field))
+    goto error;
   if (thd->variables.sql_mode & MODE_ONLY_FULL_GROUP_BY &&
       !outer_fixed && !thd->lex->in_sum_func &&
       select &&
@@ -9503,7 +9504,8 @@ bool Item_default_value::fix_fields(THD *thd, Item **items)
       Even if DEFAULT() do not read tables fields, the default value
       expression can do it.
     */
-    fix_session_vcol_expr_for_read(thd, def_field, def_field->default_value);
+    if (def_field->default_value->fix_session_expr_for_read(thd, def_field))
+      goto error;
     if (should_mark_column(thd->column_usage))
       def_field->default_value->expr->update_used_tables();
     def_field->move_field(newptr+1, def_field->maybe_null() ? newptr : 0, 1);

sql/item.h

@@ -2924,6 +2924,12 @@ class Item_ident :public Item_result_field
   const char *db_name;
   const char *table_name;
   LEX_CSTRING field_name;
+  /*
+     NOTE: came from TABLE::alias_name_used and this is only a hint! It works
+     only in need_correct_ident() condition. On other cases it is FALSE even if
+     table_name is alias! It cannot be TRUE in these cases, lots of spaghetti
+     logic depends on that.
+  */
   bool alias_name_used; /* true if item was resolved against alias */
   /* 
     Cached value of index for this field in table->field array, used by prep. 

sql/sql_base.cc

@@ -2040,6 +2040,9 @@ bool open_table(THD *thd, TABLE_LIST *table_list, Open_table_context *ot_ctx)
   table_list->updatable= 1; // It is not derived table nor non-updatable VIEW
   table_list->table= table;
 
+  if (table->vcol_fix_exprs(thd))
+    goto err_lock;
+
 #ifdef WITH_PARTITION_STORAGE_ENGINE
   if (unlikely(table->part_info))
   {
@@ -5290,52 +5293,44 @@ static void mark_real_tables_as_free_for_reuse(TABLE_LIST *table_list)
     }
 }
 
-int TABLE::fix_vcol_exprs(THD *thd)
+bool TABLE::vcol_fix_exprs(THD *thd)
 {
+  if (pos_in_table_list->placeholder() || !s->vcols_need_refixing ||
+      pos_in_table_list->lock_type < TL_WRITE_ALLOW_WRITE)
+    return false;
+
+  DBUG_ASSERT(pos_in_table_list != thd->lex->first_not_own_table());
+
+  bool result= true;
+  Security_context *save_security_ctx= thd->security_ctx;
+  Query_arena *stmt_backup= thd->stmt_arena;
+  if (thd->stmt_arena->is_conventional())
+    thd->stmt_arena= expr_arena;
+
+  if (pos_in_table_list->security_ctx)
+    thd->security_ctx= pos_in_table_list->security_ctx;
+
+
   for (Field **vf= vfield; vf && *vf; vf++)
-    if (fix_session_vcol_expr(thd, (*vf)->vcol_info))
-      return 1;
+    if ((*vf)->vcol_info->fix_session_expr(thd))
+      goto end;
 
   for (Field **df= default_field; df && *df; df++)
     if ((*df)->default_value &&
-        fix_session_vcol_expr(thd, (*df)->default_value))
-      return 1;
+        (*df)->default_value->fix_session_expr(thd))
+      goto end;
 
   for (Virtual_column_info **cc= check_constraints; cc && *cc; cc++)
-    if (fix_session_vcol_expr(thd, (*cc)))
-      return 1;
-
-  return 0;
-}
-
-
-static bool fix_all_session_vcol_exprs(THD *thd, TABLE_LIST *tables)
-{
-  Security_context *save_security_ctx= thd->security_ctx;
-  TABLE_LIST *first_not_own= thd->lex->first_not_own_table();
-  DBUG_ENTER("fix_session_vcol_expr");
+    if ((*cc)->fix_session_expr(thd))
+      goto end;
 
-  int error= 0;
-  for (TABLE_LIST *table= tables; table && table != first_not_own && !error;
-       table= table->next_global)
-  {
-    TABLE *t= table->table;
-    if (!table->placeholder() && t->s->vcols_need_refixing &&
-         table->lock_type >= TL_WRITE_ALLOW_WRITE)
-    {
-      Query_arena *stmt_backup= thd->stmt_arena;
-      if (thd->stmt_arena->is_conventional())
-        thd->stmt_arena= t->expr_arena;
-      if (table->security_ctx)
-        thd->security_ctx= table->security_ctx;
+  result= false;
 
-      error= t->fix_vcol_exprs(thd);
+end:
+  thd->security_ctx= save_security_ctx;
+  thd->stmt_arena= stmt_backup;
 
-      thd->security_ctx= save_security_ctx;
-      thd->stmt_arena= stmt_backup;
-    }
-  }
-  DBUG_RETURN(error);
+  return result;
 }
 
 
@@ -5500,9 +5495,7 @@ bool lock_tables(THD *thd, TABLE_LIST *tables, uint count,
     }
   }
 
-  bool res= fix_all_session_vcol_exprs(thd, tables);
-  if (!res)
-    res= thd->decide_logging_format(tables);
+  const bool res= thd->decide_logging_format(tables);
 
   DBUG_RETURN(res);
 }

sql/sql_partition.cc

@@ -5548,7 +5548,6 @@ that are reorganised.
         my_error(ER_ROW_IS_REFERENCED, MYF(0));
         goto err;
       }
-      tab_part_info->num_parts-= num_parts_dropped;
     }
     else if (alter_info->partition_flags & ALTER_PARTITION_REBUILD)
     {
@@ -6214,8 +6213,6 @@ static bool mysql_drop_partitions(ALTER_PARTITION_PARAM_TYPE *lpt)
   char path[FN_REFLEN+1];
   partition_info *part_info= lpt->table->part_info;
   List_iterator<partition_element> part_it(part_info->partitions);
-  uint i= 0;
-  uint remove_count= 0;
   int error;
   DBUG_ENTER("mysql_drop_partitions");
 
@@ -6230,16 +6227,6 @@ static bool mysql_drop_partitions(ALTER_PARTITION_PARAM_TYPE *lpt)
     lpt->table->file->print_error(error, MYF(0));
     DBUG_RETURN(TRUE);
   }
-  do
-  {
-    partition_element *part_elem= part_it++;
-    if (part_elem->part_state == PART_IS_DROPPED)
-    {
-      part_it.remove();
-      remove_count++;
-    }
-  } while (++i < part_info->num_parts);
-  part_info->num_parts-= remove_count;
   DBUG_RETURN(FALSE);
 }
 

sql/table.h

@@ -1404,6 +1404,12 @@ struct TABLE
   */
   bool auto_increment_field_not_null;
   bool insert_or_update;             /* Can be used by the handler */
+  /*
+     NOTE: alias_name_used is only a hint! It works only in need_correct_ident()
+     condition. On other cases it is FALSE even if table_name is alias!
+     It cannot be TRUE in these cases, lots of spaghetti logic depends on that
+     (TODO).
+  */
   bool alias_name_used;              /* true if table_name is alias */
   bool get_fields_in_item_tree;      /* Signal to fix_field */
 private:
@@ -1607,7 +1613,7 @@ struct TABLE
                                       TABLE *tmp_table,
                                       TMP_TABLE_PARAM *tmp_table_param,
                                       bool with_cleanup);
-  int fix_vcol_exprs(THD *thd);
+  bool vcol_fix_exprs(THD *thd);
   Field *find_field_by_name(LEX_CSTRING *str) const;
   bool export_structure(THD *thd, class Row_definition_list *defs);
   bool is_splittable() { return spl_opt_info != NULL; }