Mysql database: use the show profile command to analyze performance

1、show profile The role of ：

Be able to find out the recently executed SQL The running state of the statement , This includes what was done during the run , How much time did each take , utilize proflie function , Can analyze one SQL What is the specific implementation cost , In particular, we can analyze its biggest bottleneck . at present profile The function can provide statistics of resource consumption other than memory , for example CPU、I/O、CONTEXT、SWAP etc. . In most cases ,profile We mainly focus on two columns ：Status、Duration, The former means profile State in , The latter is the time-consuming of this state . therefore , Our main concern is to focus on which state it takes the longest , In these States , What can be further optimized .

2、show profile grammar ：

SHOW PROFILE [type [, type] … ] [FOR QUERY n] [LIMIT row_count [OFFSET offset]] type Parameters ： | ALL： Show all overhead information | BLOCK IO： Blocked I / O times | CONTEXT SWITCHES： Context switching related overhead information | CPU： Show CPU Related overhead information | IPC： Overhead information related to receiving and sending messages | MEMORY ： Show memory related overhead , Is useless | PAGE FAULTS ： Display page error related overhead information | SOURCE ： List the function name corresponding to the corresponding operation and its call location in the source code ( Row number ) | SWAPS： Show swap Cost information related to the number of exchanges LIMIT row_count Clause is used to limit the number of output rows .

3、show profile / show profiles Use ：

show profile as well as show profiles Statement can display the sql Statement performance (profiling) Information .

（1）profiling Function by MySQL Session variables : profiling control , The default is OFF The closed position , View the current session Open or not profile function ：

select @@profiling; show variables like ‘profiling’;

（2） Turn on profiling：

set profiling=ON;

（3） function SQL：

Just run a few SQL, In order to show profiles Log analysis of .

（4） View results ：

（4.1）show profiles

show profiles Displays the most recent statements sent to the server , The number of entries depends on the session variable profiling_history_size Definition , The default is 15, The maximum value is 100. Set to 0 Equivalent to closing profiling Analysis function . except SHOW PROFILE and SHOW PROFILES outside , all sql The performance information of the statements will be recorded , Even the wrong statement .

show profiles;

（4.2）show profile

It is used to analyze the last executed sql Statement's detailed resource usage information and working status , The default display states and their duration .

show profile;

You can give show profile To specify a for query id To see the designated id The sentence of , You can also add new columns to the output . Such as , View users and CPU Use . You can use the following command .（ For detailed parameters, please refer to section 2 Dot type Parameters ）

show profile cpu,block io for query id;

id by show profiles Of a record found Query_ID.

4、 Scope of action ：

（1） This command only works in this session , That is, statements outside this session cannot be parsed . After the analysis function is enabled , All statements in this session are parsed （ Even execute the wrong statement ）, except SHOW PROFILE and SHOW PROFILES Two sentences themselves .

（2）profiling It's conversational , When the conversation ends , Related to it profiling Information will disappear with it .

（3）profiling Is for the process (process) Not threads (threads), Therefore, other service processes running on the server may affect the analysis results .

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