[TYPO3-mvc] Question regarding argument mapping

[Jan Kornblum]

Hi group,

i'm still new to extbase (but like it more an more) and therefore i've 
a question regarding the argument-mapping machanism, which i've read 
about.

under which circumstances does extbase automatically retrieve objects 
from the repository inside a controller action? as far as i understand, 
extbase tries to retrieve an certain object from db as soon as an 
identity-parameter is set in the get/post request. right?

so when there is e.g. a showAction + this action is being called with 
tx_ext[uid]=123, extbase retrieves the corresponding object 
automatically form database.

so when i want to retrieve the object manually from the repository, i 
just must not call the controller action with an identity-parameter, 
also right? (just to prevent double requests to repository)

independent from above, when a user manipulates the get/post-request 
and adds a identity-parameter, extbase would try to ask the repository 
for this object. and can this request to repository can't be prevented?

Nice weekend, Jan