Why does pacman lock the database during downloads?

Question

Something that's always irked me about pacman is the fact that it locks the package database during the download stages of package installation, before anything has actually been installed/committed. Is there a reason for this, and if not, would a suggestion/patch be acceptable?
Here's the scenario I'm encountering right now:
* Downloading large package in background
* Need to upgrade flash player (YouTube no longer accepts an older version I suppose, and lolcats are a necessity)
* I cannot do this quick upgrade due to the lock pacman has on the database while downloading said large package
Last edited by itsbrad212 (2012-03-24 00:36:31)

Answer 1

krigun wrote:
Sounds reasonable, but the following scenario may or may not be a problem:
You have package A B and C installed:
Run pacman -Syu (huge download, all three packages updated)
Simultaneously, you execute pacman -R A (basically modify the pacman DB)
Package A updated (reinstalled) by first process
Not sure how pacman is built, but it probably locks and reads the DB when started, and then does it's thing without worries. In any case, it does support resuming downloads, so you could just end the long running process, install whatever, and resume.
I think it's the same with apt-get.
That's an interesting point, although I'm guessing the package manager could check to make sure that all packages that it wants to update are present on the system right after it locks the db, and if for some (rare) reason that one is missing, skip it.
hadrons123 wrote:
What is that large package which you think is that big?
I think locking is present in all package managers in all distributions and it is  a good Idea, so that someone can't install and uninstall a package at different terminals at the same time, and end up with a messed up package manager .
Well in this case, it is eclipse (>200 MB), but there are a variety of other large packages in the repositories. What may be small to you may seem massive to those with slower connections.
How could it become messed up? I'm not proposing the database lock be eliminated, but rather wait until the actual installation process begins before locking it. It's no skin off anybody's ass if someone simply downloads packages simultaneously.