单项选择题
You want to start monitoring statistics on the distribution of storage engines that are being used and the average sizes of tables in the various databases.
Some details are as follows:
The Mysql instance has 400 databases. Each database on an average consists of 25-50 tables. You use the query:
SELECT TABLE_SCHEMA, 'ENGINE', COUNT (*), SUM(data_length) total_size FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE= 'BASE TABLE' GROUP BY TABLE_SCHEMA, 'ENGINE' ;
Why is this query slow to execute?（）
A.Collecting information requires large numbers of locks on various INFORMATION_SCHEMA tables
B.Aggregating details from various storage engine caches for the final output is time consuming
C.Collecting information requires various disk-level operations and is time consuming
D.Counting and summarizing all table pages in the InnoDB shared tablespace is time consuming
相关考题
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多项选择题
Which two are correct steps in taking a binary backup of MyISAM tables?（）
A.Always stop the server prior to the backup
B.Stop the server or lock the tables prior to the backup
C.Stop the server or lock the databases prior to the backup
D.Make a copy of the .frm, .myd, and the .myi files
E.Make a copy of the binary log and tablespace files -
单项选择题
Which statement is true about FLUSH LOGS command?（）
A.It requires the RELOAD, FILE, and DROP privileges
B.It closes and reopens all log files
C.It closes and sends binary log files to slave servers
D.It flushes dirty pages in the buffer pool to the REDO logs -
单项选择题
Identify a performance impact when using the Performance Schema.（）
A.There is no impact on performance
B.The overhead depends on the settings of the Performance Schema
C.There is an overhead for querying the Performance Schema but not for having it enabled
D.There is a constant overhead regardless of settings and workload
