29
Jun

Profiling with MySQL

categories Computer, MySQL, Tutorials    

Whenever you encounter a query slower than you expected, and you’re sure you’ve done everything in your power to ensure your tables are properly optimized and indexed, you might want to profile it. MySQL has an inbuild profiler, which allows you to see very detailed for what part of the query how much time has been spend.

To use it, follow these steps:

(1) Activate the profiler.

Since the profiler is deactivated by default we first have to start it.

SET profiling = 1;

(2) Execute your query.

(3) Find out the query id for profiling.

SHOW PROFILES;

It will return you something like this:

    Query_ID |  Duration | Query
    ---------+-----------+-----------------------
      ...    | ...       | ...    
       29    | 0.0006200 | SHOW STATUS
       30    | 0.3600000 | SELECT (your query here)
      ...    | ...       | ...

Now you know the query id is 30.

(4) Profile the query.

SHOW PROFILE FOR QUERY 30;   // example 

This will return you the details, which might look like this:

    Status                          | Duration
    --------------------------------+-------------------
    starting                        | 0.000010
    checking query cache for query  | 0.000078
    Opening tables                  | 0.000051
    System lock                     | 0.000003
    Table lock                      | 0.000008
    init                            | 0.000036
    optimizing                      | 0.000020
    statistics                      | 0.000013
    preparing                       | 0.000015
    Creating tmp table              | 0.000028
    executing                       | 0.000602
    Copying to tmp table            | 0.000176
    Sorting result                  | 0.000043
    Sending data                    | 0.080032
    end                             | 0.000004
    removing tmp table              | 0.000024
    end                             | 0.000006
    query end                       | 0.000003
    freeing items                   | 0.000148
    removing tmp table              | 0.000019
    closing tables                  | 0.000005
    logging slow query              | 0.000003
    cleaning up                     | 0.000004

In this example, most of the time was actually spend sending the data from the server back to the client. Maybe try narrowing down the amount of data you get from the query. Maybe raise your query cache. Maybe do something different – its entirely up to your database, server and needs what to make of this result. But now you know where to look!

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Comments (1) - “Profiling with MySQL”

  1. Confluence: Claudia Malzer am 08.03.2018 um %I:%M %p Uhr 

    mysql

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