Le mercredi 05 octobre 2016 21:51:03, vous avez écrit : > On 05-10-16 17:17, Even Rouault wrote: > > Does such behaviour of files on network shares on Windows ring a bell to > > someone ? I tried (quickly) to find if this was a documented behaviour > > but didn't manage to find. > > Hi Even, well this rang with me: > > https://hub.qgis.org/issues/6448 > > it's an old discussion about reading shapefiles over a Windows network... > > And it was also talking about VSI_CACHE, and I also (from the issue) had > a little chat with Frank W about it: > > http://irclogs.geoapt.com/gdal/%23gdal.2012-07-25.log > > HTH maybe
Thanks for the pointers. Helpful indeed. The situation has changed since now QGIS opens the shapefile handle of the QgsOgrProvider object in read-only mode by default (used to be read-write before latest 1.16 and 1.14 point releases), hence I'm wondering if the VSI_CACHE mechanism has still some effect on the read-only handles owned by the QgsOgrFeatureIterator objects, which are the ones that matter for rendering operations. Seeing https://msdn.microsoft.com/en-us/library/windows/desktop/aa365433%28v=vs.85%29.aspx which is about opportunistic locks, I would think that a read-write file handle would defeat opportunistic locks, hence the slowness seen. That would also what Radim suggested in a comment : "OpLocks are broken for read only files, not for read write files if opened as read only, at least this was observed on Windows XP + Samba" -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ Qgis-developer mailing list [email protected] List info: http://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-developer
