Re: [mysql 4.0.14-nt] MySQL eats my CPU with speical SELECT statement

Hello alexander,

thanks for your quick reply - see my comments below ...

> We will investigate this case, but Query in question is Cartesian Product between 
> 3 tables!
> 
> ...
> 305*3638*231 = 256315290

(quite impressing arithmetics, indeed :)

> 
> Query which will provide 256 million rows and which can store them in some 
> temporary space before sending to client will be always slow.

Ah, yes ... looking at the (wrongly generated) statement, again:

  SELECT `artists`.`name`, `albums`.`name`
  FROM `albums`, `tracks`, `artists`
  GROUP BY `tracks`.`al_id`
  HAVING 0 = 1

... Being *that* used to seeing "WHERE 0 = 1" in OOo-generated
statements, I didn't realize that we're talking about a HAVING here,
which of course is a different thing.

> I don't agree with you about
> "closing as INVALID, because it's an MySQL bug."

You're completely right, sorry for sueing MySQL! This, indeed, is an
amount of data which the next 4 generations of my PC won't be able to
handling easily :).

I'll state this in the IZ-issue (citing you there :), and reopen it.

> This is very good example of careless SQL usage. No matter if this query is 
> written by hand or generated by some programs.

Generated by OOo in this case, unfortunately :(. I already submitted an
issue for this improper generation, before I asked here, but as said:
reading the HAVING as WHERE didn't let me realized that it's also the
real problem. Sorry!

> Do you agree with me this is not a bug really?
Yes!

Thanks & Ciao
Frank



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