假设我们有一个名为test_db的数据库,其中包含表users和orders,我们可以使用上述SQL语句查询它们的大小: SELECTtable_nameAS`Table`,round(((data_length+index_length)/1024/1024),2)`Size in MB`FROMinformation_schema.tablesWHEREtable_schema='test_db'ORDERBY`Size in MB`DESC; 1. 2. 3. 4. 5. 6. ...
ORDER BY (data_length + index_length) DESC; """)tables=[]sizes=[]# 获取查询结果fortable,sizeincursor:tables.append(table)sizes.append(size)# 生成饼状图plt.figure(figsize=(10,7))plt.pie(sizes,labels=tables,autopct='%1.1f%%')plt.title('MySQL Table Sizes')plt.show()cursor.close()conn...
ENUM is a string object with a value chosen from a list of permitted values that are enumerated explicitly in the column specification at table creation time. See Section 13.3.1, “String Data Type Syntax” for ENUM type syntax and length limits. ...
A SET is a string object that can have zero or more values, each of which must be chosen from a list of permitted values specified when the table is created. SET column values that consist of multiple set members are specified with members separated by commas (,). A consequence of this ...
The term“index” here refers to a position within the list of enumeration values. It has nothing to do with table indexes. For example, a column specified asENUM('Mercury', 'Venus', 'Earth')can have any of the values shown here. The index of each value is also shown. ...
(If your operating system does not support files that large, table sizes are constrained by the file size limit.) If you want to keep down the pointer sizes to make the index smaller and faster and you don't really need big files, you can decrease the default pointer size by setting ...
有两种方式可以触发统计信息的采集:一种是手动执行,通过执行SQL:ANALYZE TABLE table_list来采集统计信息;另一种是系统自动执行。 系统自动收集统计信息的策略是,当表中更新的记录数超过一个阈值,(例如Persistent采样默认的阈值是总记录数的10%),就会将当前table加入统计信息采集的任务队列中,由后台线程来完成采集。
数据库实例的物理文件的大小是根据系统表计算的表大小的两倍以上,原因是统计数据不准确,具体是索引数据页的数量不准确。 引言 MySQL 的统计信息中包括多个统计项,由于基于采样计算,因此存在误差,最常见的是统计项【表的行数】不准确,可能导致执行计划选择错误。
hash_table_t *page_hash; // 页哈希表 hash_table_t *zip_hash; //伙伴系统分配frame对应的block哈希表 UT_LIST_BASE_NODE_T(buf_page_t) free; //空闲链表UT_LIST_BASE_NODE_T(buf_page_t) LRU; // LRU 链表 UT_LIST_BASE_NODE_T(buf_page_t) flush_list; // flush 链表 ...
Previously when using the MySQL Administrator & Query Browser Tools we could view the table sizes growing when hitting a "Refresh" button and it was great to see the various table sizes growing (kb) as items were being Inserted into tables. ...