It is already being looked at. If you had looked at the bug list on the Calibre project page (
https://bugs.launchpad.net/calibre2opds) you would see that this is down as an "in progress" item. The way we are intending to implement this feature is to let the main generation happen unchanged to the TEMP folder on the local machine. The Copy phase is then optimised to avoid copying any newly generated files whose content is identical to the previous run. This approach is being used as detecting that a file WOULD be unchanged before we even attempt to generate it is too hard..
The current status is that the code to this in place and appears to work. Items intended to complete this change are:
- Make it an optional feature. At the moment it is not optional, and as it adds to the time taken to generate the catalog all users may not want this feature on by default.
- Look at ways of reducing the costs at the catalog generation stage, possibly by cachng results during runs. We may make the first release without this being implemented so that we can get user feedback on the effectiveness of the feature in their particular environments.
Look for this feature to be avaiable therefore in beta 4.
If anyone is interested in looking at the current change without the extra work mentioned above, then they are welcome to check the source code out of launchpad and build calibre2opds on their own machine. If nothing else that would help check out how complete the documentation (
https://wiki.mobileread.com/wiki/Calibre2OpdsDevelop) is for setting up ones own development environment for calibre2opds.