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From:Michael Dykman Date:October 9 2011 5:06am
Subject:Re: optimizer in function
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I think the only clues the optimizer consults with regard to UDFs is the
'characteristic' provided at the time you create the routine.

from http://dev.mysql.com/doc/refman/5.0/en/create-procedure.html
*

*

*characteristic*:
    COMMENT '*string*'
  | LANGUAGE SQL
  | [NOT] DETERMINISTIC
  | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
  | SQL SECURITY { DEFINER | INVOKER }


 - michael dykman
2011/10/8 Halász Sándor <hsv@stripped>

> Does the optimizer look into function called from query?
>
> In my queries the expression (SELECT hwyl FROM Stock) / (SELECT
> regularPayment FROM Stock), where Stock is a one-record table, often is
> repeated. The optimizer sees that, and makes the ratio a constant, and I can
> afford to be clear. If that expression were within a function called from
> the same spot, would the optimizer look into the function and see the same
> effectiv constant? or is it better to make it an argument to the function?
>
>
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-- 
 - michael dykman
 - mdykman@stripped

 May the Source be with you.

Thread
optimizer in functionhsv9 Oct
  • Re: optimizer in functionMichael Dykman9 Oct