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From:mos Date:August 30 2002 4:04pm
Subject:Re: RE: performance tunning 4.x
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At 07:58 AM 8/30/2002, you wrote:
>mos,
>Thursday, August 29, 2002, 5:45:05 PM, you wrote:
>
> >>Start by looking at the MySQL documentation:
> >>http://www.mysql.com/doc/en/Query_Cache.html
> >>Read the entire 6.9 section.
> >>
> >>It offers quite a bit of information on how the cache operates, how
> >>you should configure it and so on.
>
>m>          I read it too but I have a question about the cache, this sentence
>m> in particular.
>
>m>  NOTE: The query cache does not return stale data. When data is modified,
>m> any relevant entries in the query cache are flushed.
>
>m> If I have a select statement like:
>
>m> select col1, col2 from table1 where col1='A'
>
>[skip]
>
>m> c) Or will any update to the table automatically flush the cache?

Victoria,

>Yes, relevant entries in the query cache are flushed when any changes were 
>made on the
>table.

Can you define "relevant"? Do you mean all caches for that table?

Are you saying any change at all to the table, say I add a row, delete a 
row, or modify a row even if it is not in the scope of the cached query, 
will cause all caches for that table to be discarded? Argghhh! :-O

Example:

select customer_name from customers where state = 'NY'  //<-Adds query to cache

insert into customers (customer_name, state) values('jones', 
'CA')  //<-Flushes the cache for customers table?

select customer_name from customers where state = 'NY'  //<-No longer in cache?

If you are correct, then I feel caching is useful primarily for readonly 
access to a table. As soon as a row is modified in any way, the caches for 
that table are flushed. Would you agree?

Mike

Thread
performance tunning 4.xSean Hager28 Aug
  • Re: performance tunning 4.xIikka Meriläinen28 Aug
    • RE: performance tunning 4.xSean Hager28 Aug
      • RE: performance tunning 4.xIikka Meriläinen28 Aug
        • RE: performance tunning 4.xmos29 Aug
          • Installing mysql 4.0.3 with linux threads on freebsdVarshavchick Alexander29 Aug
            • Re: Installing mysql 4.0.3 with linux threads on freebsdDan Nelson29 Aug
              • Re: Installing mysql 4.0.3 with linux threads on freebsdVarshavchick Alexander30 Aug
            • limiting the userSoheil Shaghaghi30 Aug
              • limiting the userSoheil Shaghaghi1 Sep
                • RE: limiting the userDean Harding1 Sep
          • RE: performance tunning 4.xIikka Meriläinen29 Aug
          • Re: RE: performance tunning 4.xVictoria Reznichenko30 Aug
            • Re: RE: performance tunning 4.xmos30 Aug
              • Re: RE: performance tunning 4.xPaul DuBois30 Aug
              • Re: Re: RE: performance tunning 4.xVictoria Reznichenko31 Aug