I just upgraded my galeries and I had no big problem.
I got some queries errors but it was due to my header file that etablished MySQL connexions and conflicted with PP, so I had to force to open new connexions like that :
So I suggest to everyone who has upgrade problems to remove custom header and footer files.
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I just have a question about this new version : what is exactly the new parameter "Use photo view caching to reduce view update queries on high load sites
Should I enable this feature ?