Comment by izacus
That's much more likely flash degradation than actual fragmentation. Did you use cheap tablets with eMMC storage?
That's much more likely flash degradation than actual fragmentation. Did you use cheap tablets with eMMC storage?
Yeah, then copying the files most likely moved them to different part of storage and it improved performance again.
Sadly that's a common plague for cheaper Android hardware - after enough writes the flash performance drops off a cliff making those devices essentially unusable :/
(More expensive hardware - including Apples - tends to have UFS type storage which lasts longer.)
We had that thought too. I'll have to try dig out what the tablets were to find out exactly what type - this would have been 3 or 4 years ago now. We sort of ruled that out because:
The other workaround to get a speed boost was the user to uninstall and reinstall the app (and then wait for all the data to download again) but that didn't fly because the users would delete before they'd synced off all their data and then data would go missing.
This was all despite having VACUUM running whenever the app started.
Whether it was bad flash or no, we still had to try resolve it as the client wouldn't buy new hardware until we could prove that we had the knowledge to make the problem go away first :/
> That's much more likely flash degradation than actual fragmentation. Did you use cheap tablets with eMMC storage?
My understanding of the parent reply's situation is that this was happening on the tablets of their users, so it kinda doesn't matter that it can be avoided by not using cheap tablets.
Most apps aren't in a position to tell their users that they are on their own when they run into what feels like an unreasonable app slowdown because they didn't buy a good enough device to run it on, especially when they've previously experienced it running just fine.
If all their apps feel like crap on that tablet, sure, that might fly... but if its only your app (or only a small set of apps that use SQLite in the same way the OP's company did) that feels like crap after a while, that's effectively a you problem (to solve) even if its not really a you problem.
In any case, its an interesting data point and could be very useful information to others who run into similar issues.
I don't quite understand what you're arguing here.
I'm merely saying that the root cause was misidentified - the performance degradation didn't happen due to fragmentation, but because the flash storage was degraded to the point where the write performance dropped significantly. This happens faster for eMMC vs. SSD-style storage.
Copying the DB file moved the data to different storage blocks which is why it (temporarily again) improved performance.
Ah yup eMMC https://www.gsmarena.com/samsung_galaxy_tab_active2-8897.php