[gdal-dev] Reading SQLite in WAL mode as read-only

[Even Rouault]

On samedi 4 mars 2017 16:26:35 CET Rahkonen Jukka (MML) wrote:
> Hi,
> 
> I saw this changeset https://trac.osgeo.org/gdal/changeset/37594 and started
> to think that how  GDAL is reading SQLite db that is in WAL journal mode
> from zip, tar, vsicurl or from non-writeble directory if it is documented
> to be generally not possible http://www.sqlite.org/draft/wal.html?

The official page is at
https://www.sqlite.org/wal.html

"5. It is not possible to open read-only WAL databases. The opening process must have write 
privileges for "-shm" wal-index shared memory file associated with the database, if that file 
exists, or else write access on the directory containing the database file if the "-shm" file 
does not exist. "

I'm trying to optimize the speed of 
ogrinfo -ro /vsitar/my.tar.gz/my.gpkg
on very large files
(but it turns out to be much more involved, since it requires system records to be contained 
at the beginning of the file)

-- 
Spatialys - Geospatial professional services
http://www.spatialys.com
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