UDSEntry compression ideas

[Frank Reininghaus]

Hi Mark,

I'm too tired for a longer reply already, but here is a quick idea
that I just had and tried immediately.

2013/9/16 Mark:
> Hi All,
>
> please read this as a brainstorm post with some ideas. I have no code
> working in this area yet.
>
> Lazy loading is awesome, but if you can compress the data enough that you
> still have all details without lazy loading is even better i think. For
> example, doing a directory listing on any given folder gives at least the
> following UDSEntry values:
> - Device ID
> - Inode
> - User
> - Group
>
> In the "experimental" case where you list the folder contents that has just
> a bunch of files created by one user you can say that at least the above 4
> properties are the same for all files. However, the experimental situation
> certainly doesn't work on "real data" where you can have files from multiple
> users and folders as well.

Well, I guess that most people have quite a few folders where the
"User" and "Group" are the same for all files ;-)

The easiest "compression" that I could think of was to force the
UDSEntries to implicitly share all their QStrings for one field if
they are all equal:

http://paste.kde.org/p52a24b49/

Reduces the memory consumption in Details View for 100,000 items from
160.5 MB to 147 MB here. The patch is a bit hackish though, and it
might have a small performance penalty. Maybe it's worth investigating
that further though.

I guess any more sophisticated "compression" approach will have to be
implemented in frameworks only.

Cheers,
Frank