Pb importing data in a custom collection

[Marcelin Jose-Marcio Martins da Cruz]

Hello,

I've created a custom collection, a collection of photographs (many 
thousands). I'm filling it thanks to .CSV data files.

But, each time I add new photographs, I need two steps : the first one 
to create new entries with some fields and the second one to add other 
fields (EXIF data). Unfortunately, I can't do it in a single step.

So the first step must be adding entries (option : append to current 
collection) and the second one to update these new entries (option : 
merge to current collection). The first step works fine, but the second 
one does nothing.

Maybe I'm doing something wrong. Is there a key field which must be 
present in both files ?

Maybe you can have a suggestion ?

Thanks in advance.

José-Marcio