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As the title says, I'm wondering what is this command and why am I seeing a large amount of this query on my database? It's currently 13.30% of my total queries. I've tried googling this but there's not really any documentation on the subject.

Here's a part of the report done by mysqlreport:

__ Questions ___________________________________________________________
Total          17.43M     7.5/s
  DMS           8.58M     3.7/s  %Total:  49.23
  QC Hits       3.91M     1.7/s           22.42
  Com_          2.54M     1.1/s           14.54
  COM_QUIT      2.48M     1.1/s           14.21
  -Unknown     68.28k     0.0/s            0.39
Slow 10 s          17     0.0/s            0.00  %DMS:   0.00  Log:  ON
DMS             8.58M     3.7/s           49.23
  SELECT        6.05M     2.6/s           34.71         70.51
  INSERT        1.36M     0.6/s            7.80         15.85
  UPDATE        1.15M     0.5/s            6.60         13.40
  DELETE       20.35k     0.0/s            0.12          0.24
  REPLACE          61     0.0/s            0.00          0.00
Com_            2.54M     1.1/s           14.54
  set_option    2.32M     1.0/s           13.30
  show_proces  83.16k     0.0/s            0.48
  create_tabl  60.20k     0.0/s            0.35
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up vote 3 down vote accepted

It probably means that you ran a lot of commands that start with "SET something = somethingelse;"

I would say to set your general_log on for a short while on your dev environment and search for SET commands. It would probably be something to do with setting the server time.

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Thanks, figured out this was because of SET NAMES utf8. – onik Sep 14 '11 at 8:13
Actually COM_SET_OPTION is used exclusively for multi-statement support as explained here. SET commands issued by clients are just sent as regular queries, so something like SET NAMES utf8 would not generate a COM_SET_OPTION packet. – Michael Mior Dec 17 '14 at 23:04

COM_SET_OPTION is a special command in the MySQL protocol which is currently used exclusively to enable or disable multi-statement support as detailed here. Some database clients (such as certain versions of the MySQL libraries for PHP) will do this every time a new connection is established.

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