[TYPO3-english] Duplicate cHash values

[Dan Osipov]

 > But I think it is axiom: less data and shorter keys -> more speed to 
SELECT.

Sure, but the question is by how much. It doesn't matter that the look 
up is fast if it gives the wrong result. So its a trade off between 
accuracy and speed - and in this case I think accuracy takes priority.

Dan Osipov
Calkins Media
http://danosipov.com/blog/

Dmitry Martynenko wrote:
> Hi Dan,
> 
> DO> I think the 32 char value must be used, to prevent collisions and
> DO> guarantee (almost) the uniqueness. How slow does it make the table 
> DO> seeks? And what table are we talking about - I think 
> DO> tx_realurl_chashcache only looks up by spurl_hash.
> 
> I write yesterday about it in another thread, quotation below.
> 
> -----------------------------------------------------------------
>  Our server begun to increase time for all SQL queries and
>  I try to log slow queries (> 100 ms) from class.t3lib_db.php
> 
>  Most of them was like:
>  SELECT /*! SQL_NO_CACHE */ content
>  FROM tx_realurl_urlencodecache
>  WHERE url_hash='43d5475f5d7dc35690cb8ab3d7683679' AND tstamp>1232035875
> 
>  This table has more then 450 000 records.
>  It's  index size greater than 30 Mb.
>  I think big index size and long key length take lot of time to search.
> -----------------------------------------------------------------
> 
> May be it is need more testing.
> But I think it is axiom: less data and shorter keys -> more speed to SELECT.
>