I know in california if it is a Schedule 2 narcotic, the Pharmacy keeps the original script on file for a certain amount of time.
I also know that in California, lets assume you got a script filled at Wallgreen and then on day 26 you take your new script to CVS, so long as your a cash paying patient, they will not have any way of knowing you filled a script at another pharmacy even if it is a Sch II.
Now if your insurance is one file, then based on your insurance showing your last fill, they will of course know when you last got a fill.
Regardless if you get a script and even if it is through insurance and your doctor allows for a vacation override, 95% percent of insurances and pharmacies would allow for the script to be filled. Especially if it is only a few days away from when it was scheduled to be filled anyways.
If you live in California and you just want to go pay cash and go to a different pharmacy then where your last script was filled, I would not worry about the phramacy having a record of any scripts you filled at a different pharmacy. (Maybe other states do have a database, but definitely not California)
Just make sure whichever pharmacy you go to, that they do not have your insurance card on file, otherwise they will automatically run it and will know when your last script was filled.
Again if you are only talking about getting your script filled a few days early and your doctor knows all about you getting it filled early. Then I would not stress about going into another Pharmacy and having the pharmacy say "Hey pal your a few days early", worst case you answer and say "Yes, I know that, but I'm going on vacation and my doc says that I can get my script filled right now, you can even call the office to confirm"
Hope this helps.