[Qgis-user] Something to think about GeoPackage and WAL

[jratike80]

I believe that for most users and most of the time using WAL does not make
any harm. What I can imagine affects mostly eager power users who might

1) Take only the .gpkg file and copy it while GeoPackage is still open in
QGIS - Hey, I have been reading that GeoPackage is just one file! As a
results the copy of GeoPackage lacks the pending edits and it remains in WAL
mode.

2) Keep GeoPackage open in other programs (like spatialite-gui) while it is
also open in QGIS. If QGIS is closing the connection first it can't switch
the journal mode, and if the other program does not even try to switch the
mode the GeoPackage file will remain in WAL mode. Data loss will not happen,
though.

Some real harm may happen if data are delivered for end users as GeoPackage
that is in WAL mode. If the WAL-db is saved into read-only media (CD, DVD,
read-only memory card) it can't be opened at all before copying it into some
writable media. And if user is placing the WAL db on a network drive it may
lead to some other problems in multi-user environment.

Probably this kind of issues will not occur frequently and I can't say if
enabling WAL by default makes more harm than good. 

-Jukka Rahkonen-


Even Rouault-2 wrote
> If the current situation causes more harm than good, we can change the 
> "/qgis/
> walForSqlite3" setting default value to false. Together with enabling WAL,
> I made another 
> change in the OGR provider that prevented a reader that has finished from
> iterating over 
> features from being left in a ghost active state, but I guess there will
> be real read/write 
> concurrent situations were deadlocks will appear.





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