From: Sergei Golubchik
Date: May 15 2009 12:19pm
Subject: Re: Question on parser and variable
List-Archive: http://lists.mysql.com/internals/36702
Message-Id: <20090515121926.GB10158@janus.mylan>
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Hi, Joseph!

On May 14, Joseph Lukas wrote:
> So far I have the parser looking at mysql_set_variable as a SELECT
> <option> and it can make it past the parser so long as you do not use
> a *. 
...
> I was going to ask if I could move the command out in front of the
> select as it seems to get confusing with the select terms.  Such as
> 
> MYSQL_SET_VARIABLE sort_buffer_size=100000 SELECT * FROM test;
...
> I like version 2 better it just looks simpler and better defined with less
> chances for user error. Yes/no

Actually, the specs in WL#681 have four different syntax variants.
What you started implementing is #1, what you want to switch to is #3.

I'll describe #3 again. The syntax is:

  SET STATEMENT sort_buffer_size=100000 SELECT * FROM test;

which vaguely resembles

  SET GLOBAL sort_buffer_size=100000;
  
and

  SET SESSION sort_buffer_size=100000;

so it's not completely new for MySQL users.
Note also:

* more than one variable can be set:

  SET STATEMENT sort_buffer_size=100000, record_buffer=10000 SELECT * FROM test;

* for the compound statement:

  SET STATEMENT sort_buffer_size=100000 BEGIN SELECT * FROM test; END

  the new value is set till the END of the compound statement.

* the statement is completely parsed first, then executed. that is

  SET STATEMENT sql_mode=ANSI DROP TABLE "t"

  won't work.

Regards / Mit vielen Grüßen,
Sergei

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