[TYPO3-dev] Testing TYPO3 caching vs.[FE][pageCacheToExternalFiles]

["Marc Wöhlken [quadracom]"]

Martin Schoenbeck schrieb:
> Why do you and other think, explain wouldn't know how indexes will be used?
Probably our opinions are quite close together as I do think mysql
explain does know what indexes it could / should use.


> So explain exactly tells whether and how an index will be used.
It does only indicate whether or not indexes are used BUT NOT if a query
will benefit from them!

>> AFAIK indexes are for example not used for disk i/o if the result
>> contains more than 1/3 of the total datasets as a complete read of the
>> corresponding db file should be faster than doing random disk acces
>> based on indexes.
> 
> Maybe, but then explain will tell exactly that.
That's not quite true as explain does not take into account the stored
data. Explain just works on the table structure and indexes.

>There are really situations
> where a full table scan is nothing bad. But because that depends on the
> data you can't do index optimization for all situations. What you typically
> can do is an optimization which works for big sites and then verify that it
> doesn't hurt small sites.
FULL ACK.

CU
 Marc

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Marc Wöhlken

Quadracom - Gottschall, Proffe & Wöhlken

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