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这篇文章主要介绍“怎么使用MySQL中的参数binlog_row_image”，在日常操作中，相信很多人在怎么使用MySQL中的参数binlog_row_image问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”怎么使用MySQL中的参数binlog_row_image”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
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插入前先调用TABLE::mark_columns_per_binlog_row_image函数
函数中有image的详细设置
/*
Mark columns according the binlog row image option.
When logging in RBR, the user can select whether to
log partial or full rows, depending on the table
definition, and the value of binlog_row_image.
Semantics of the binlog_row_image are the following
(PKE - primary key equivalent, ie, PK fields if PK
exists, all fields otherwise):
binlog_row_image= MINIMAL
- This marks the PKE fields in the read_set
- This marks all fields where a value was specified
in the write_set
binlog_row_image= NOBLOB
- This marks PKE + all non-blob fields in the read_set
- This marks all fields where a value was specified
and all non-blob fields in the write_set
binlog_row_image= FULL
- all columns in the read_set
- all columns in the write_set
This marking is done without resetting the original
bitmaps. This means that we will strip extra fields in
the read_set at binlogging time (for those cases that
we only want to log a PK and we needed other fields for
execution).
*/
void TABLE::mark_columns_per_binlog_row_image()
{
DBUG_ENTER("mark_columns_per_binlog_row_image");
DBUG_ASSERT(read_set->bitmap);
DBUG_ASSERT(write_set->bitmap);
/**
If in RBR we may need to mark some extra columns,
depending on the binlog-row-image command line argument.
*/
if ((mysql_bin_log.is_open() && in_use &&
in_use->is_current_stmt_binlog_format_row() &&
!ha_check_storage_engine_flag(s->db_type(), HTON_NO_BINLOG_ROW_OPT)))
{
THD *thd= current_thd;
/* if there is no PK, then mark all columns for the BI. */
if (s->primary_key >= MAX_KEY)
bitmap_set_all(read_set);
switch (thd->variables.binlog_row_image)
{
case BINLOG_ROW_IMAGE_FULL:
if (s->primary_key < MAX_KEY)
bitmap_set_all(read_set); //记录全部字段
bitmap_set_all(write_set); //记录全部字段，前面write_set应该只是记录了 修改了哪些字段 位图 初始化初始4字节
break;
case BINLOG_ROW_IMAGE_NOBLOB:
/* for every field that is not set, mark it unless it is a blob */
for (Field **ptr=field ; *ptr ; ptr++)
{
Field *my_field= *ptr;
/*
bypass blob fields. These can be set or not set, we don't care.
Later, at binlogging time, if we don't need them in the before
image, we will discard them.
If set in the AI, then the blob is really needed, there is
nothing we can do about it.
*/
if ((s->primary_key < MAX_KEY) &&
((my_field->flags & PRI_KEY_FLAG) ||
(my_field->type() != MYSQL_TYPE_BLOB)))
bitmap_set_bit(read_set, my_field->field_index);
if (my_field->type() != MYSQL_TYPE_BLOB)
bitmap_set_bit(write_set, my_field->field_index);
}
break;
case BINLOG_ROW_IMAGE_MINIMAL:
/* mark the primary key if available in the read_set */
if (s->primary_key < MAX_KEY)
mark_columns_used_by_index_no_reset(s->primary_key, read_set); //只记录主键或者非空唯一键的 字段
break;
default:
DBUG_ASSERT(FALSE);
}
file->column_bitmaps_signal();
}
DBUG_VOID_RETURN;
}THD::binlog_prepare_row_images还会准备image
binlog_log_row 上层接口 记录 binlog -> Write_rows_log_event::binlog_row_logging_function -> THD::binlog_write_row(THD::binlog_delete_row) ->THD::binlog_prepare_row_images 准备前印象位图 如果没有主键/非空唯一键 则不考虑记录全字段 pack_row 通过位图准备好行 THD::binlog_prepare_pending_rows_event -> 判断是否需要新建一个EVENT 大约8K左右， 如果新建 新建后写event到 log buffer ->否则在当前event中写入 add_row_data(row_data, len); 将数据加入到EVENT
到此，关于“怎么使用MySQL中的参数binlog_row_image”的学习就结束了，希望能够解决大家的疑惑。理论与实践的搭配能更好的帮助大家学习，快去试试吧！若想继续学习更多相关知识，请继续关注创新互联网站，小编会继续努力为大家带来更多实用的文章！
