Bypass uninstall

[sabarnett]

My app is quite small and new versions can be installed over the top without the need to uninstall the previous version. I'm trying to generate an install that does not uninstall the previous version, but am failing miserably.

Is it possible to indicate that I do not want an uninstall, but want the old install to be overwritten?

Thanks
Steve

[sabarnett]

It's Ok, I worked it out. If I set the NEEDSUPGRADE variable to false in the Check Application Pre-Requisites region, the window goes away.

Thanks
Steve

[CandiceJones]

Doing so can have undesired consequences. You shouldn't do that. With MSI technology, you either want to patch an existing setup, or uninstall it and then re-install it.

If your application files are really small, you can always bypass MSI itself and commands that directly execute through the OS - such as calling CopyFileA in kernel32.dll through Call DLL Function, to install and/or overwrite files in an existing installation.

[soeinz]

Doing so can have undesired consequences. You shouldn't do that. With MSI technology, you either want to patch an existing setup, or uninstall it and then re-install it.

Can you please explain exactly why this is necessary? Our problem is that if you have a really large install there is a significant loss in performance in having to perform a complete uninstallation. Surely you would think MSI was smart enough to simply overwrite the files that had changed and leave the others alone without re-installing everything? As for patching, from what I have seen of the way it is implemented with InstallAware, the patch patches the installation files not the actual installed files so you still have to proceed through an uninstallation. I get the feeling there is something I'm not understanding or that I missing, in any case we really need to improve the performance of our installer so any help would be greatly appreciated.

[CandiceJones]

It seems like you should be using patches. What problem are you having with patches? The patch will be applied to your target installation - I'm not sure why you don't think that is the case?

[soeinz]

It seems like you should be using patches. What problem are you having with patches? The patch will be applied to your target installation - I'm not sure why you don't think that is the case?

Don't know for sure so it is an impression that we have. The patches we build take as long (sometimes longer) to run than a full install, they seem to run through the same installation process including the 'installing requirements' phase which runs through the 'previous version uninstallation' before re-installing. So it seems that although a patch is very small (which is good) what it is actually doing is patching the setup files and then re-running them, not patching the target installation directly.
Actually I think I might have just worked it out! We took out the compiler variable check above the uninstall command in the script. I'll put it back and see if it makes a difference.

[CandiceJones]

If you changed the compiler variables in the script, you may have broken patch functionality. With the default project, everything will work as expected when using patches. Read the patching whitepaper for more information on the process and how the one-click patching magic works - that also helps explain how the compiler variables are used.

[soeinz]

Hi,

I've definitely gone back and put these compiler variables in but the patch is still exceedingly slow. Our normal installer is around 400 meg and the patch comes to around 4 meg. There doesn't appear to be an uninstall step now but the patch installation does still appear to be running and modifying/copying every file which contributes to the poor performance. This combined with the fact that the patch installation requires the original setup file to run is what has led me to believe that what is was doing was patching the reference setup and then just running that. Am I right to expect a patch installation to be significantly faster than a normal installation?

[CandiceJones]

These aren't really InstallAware pre-sales questions at this stage, please keep forum posts on topic. Thank you.