Function optimize_schema_tables_memory_usage

sql/sql_show.cc:9703–9770

bool optimize_schema_tables_memory_usage(List<TABLE_LIST> &tables)
{
  DBUG_ENTER("optimize_schema_tables_memory_usage");

  List_iterator<TABLE_LIST> tli(tables);

  while (TABLE_LIST *table_list= tli++)
  {
    if (!table_list->schema_table)
      continue;

    TABLE *table= table_list->table;
    THD *thd=table->in_use;

    if (!thd->fill_information_schema_tables())
      continue;

    if (!table->is_created())
    {
      TMP_TABLE_PARAM *p= table_list->schema_table_param;
      TMP_ENGINE_COLUMNDEF *from_recinfo, *to_recinfo;
      DBUG_ASSERT(table->s->keys == 0);

      uchar *cur= table->field[0]->ptr;
      /* first recinfo could be a NULL bitmap, not an actual Field */
      from_recinfo= to_recinfo= p->start_recinfo + (cur != table->record[0]);
      for (uint i=0; i < table->s->fields; i++, from_recinfo++)
      {
        Field *field= table->field[i];
        DBUG_ASSERT(field->vcol_info == 0);
        DBUG_ASSERT(from_recinfo->length);
        DBUG_ASSERT(from_recinfo->length == field->pack_length_in_rec());
        if (bitmap_is_set(table->read_set, i))
        {
          field->move_field(cur);
          field->reset();
          *to_recinfo++= *from_recinfo;
          cur+= from_recinfo->length;
        }
        else
        {
          field= new (thd->mem_root) Field_string(cur, 0, field->null_ptr,
                                field->null_bit, Field::NONE,
                                &field->field_name, field->dtcollation());
          field->init(table);
          field->field_index= i;
          DBUG_ASSERT(field->pack_length_in_rec() == 0);
          table->field[i]= field;
        }
      }
      if ((table->s->reclength= (ulong)(cur - table->record[0])) == 0)
      {
        /* all fields were optimized away. Force a non-0-length row */
        table->s->reclength= to_recinfo->length= 1;
        to_recinfo->type= FIELD_NORMAL;
        to_recinfo++;
      }
      store_record(table, s->default_values);