Enabling timestamps and copying and pasting many entries is very slow

[ThiloteE]

Let me add another performance report: I copied the 10500 entries of my database (the message of having copied the entries came after about 1.2 seconds, fine)). Pasting it into a new empty file took about 9 minutes.
meanwhile, jabref was not usable.

I have now disabled the timestamp and repeated the operation of creating an entirely new database. copying and pasting the >10500 entries was much swifter: 23-26 seconds.

• Originally posted by @ilippert in Performance issues with version 5.0 (example videos) #5071 (comment)
• Meta issue: Meta-issue: Improve JabRef's performance - Reduce CPU / RAM usage, increase speed and detect bottlenecks #8906

JabRef 5.1--2020-05-04--7bb1e24
Linux 5.6.8-200.fc31.x86_64 amd64
Java 14.0.1

[ThiloteE]

@Christoph @calixtus

Maybe this will be fixed by your refactor of the import format reader and clipboard manager ? :-)

To do:

• try to reproduce with Refactor of DOI import failure dialog, import format reader and clipboard manager #8839
  Result: Still very slow even with timestamps disabled!
  I copy pasted 10 000 entries (timestamps disabled). I force closed JabRef 29 minutes after start, because the operation seemed to take endless. RAM remained constant. CPU was maxed out:
  

  Edit: Simply copying 500 entries very reliably takes 30 seconds on my laptop. (I did multiple tests). Doing the math, copying 10 000 entries then SHOULD take around 10 minutes, but for some reason it does take a lot longer.