[Typo3-dev] Empty cHash problem

[Elmar Hinz]

> Empty cHash problem. Empty cache is never a problem, as it can be
> filled. :) And if its empty, the empty cHash is not a problem, its just
> a problem if the cache already filled!

???

Either this is not precise enough or tells something else then the 
article. There isn't a problem when the cache is already filled in the 
article. The problem is filling the empty cache with the right stuff.

> 
> The problem, to sum up:
> 
> When generating the page that will be cached where we have our USER
> plugin. The plugin will output something based on the piVars (e.g.
> display the detail view of the current record). If we don't take any
> precaution, our output will always be cached too by TYPO3 (this is why
> we are an USER object!). So the next requests, regardless of the
> parameters, would display the same output as the first request, thus
> making our parameters useless! Only the first request after clearing the
> cache wins. 

So far it is right. Here we still have only one cache for all views.

We have to avoid that in the first call already, by only
> allowing TYPO3 to cache the output if we are sure that the parameter
> combination is something can be checked against a valid cHash.

Here seems to be a gap in your explenation. You still haven't created 
different chaches for different combinations of parameters.

By the way. Is there a special table for caching views with additional 
parameters or is it the same table as for the old id + type combination? 
Which tables are they? Wich fields in the tables?

> 
> 
>>It happens according to Kaspers article:
>>
>>a) when the cache is cleared for that page (is empty)
>>b) when the first call comes with paramters that request a special view
>>of the page
>>c) when no cHash is given
>>
>>Wouldn't it also happen when
>>
>>a) ...
>>b) ...
>>c) a cHash is given but a wrong one
> 
> 
> The article section is devoted to the case when cHash is EMPTY, so this
> case does not apply.

That is a quite philisophical answer.

> 
> Also in this case, TYPO3 will see that the cHash is not valid for the
> current parameter set and caching will be disabled altogether, which has
> the same effect as having an empty cHash.

That is exactly my thesis. The effect would be the same. Even if there 
isn't an empty cHash but an invalid one.


> 
> Cheers,
> Ernesto


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