[Qgis-developer] Fwd: Re: [Geopackage] Geopackage on a shared network drive

Mon Oct 3 03:16:35 PDT 2016

> There's the "read only" setting (hidden away) under Project Properties
> -> Identify Layers which this could potentially hook into.

Didn't know that one! I see this is done through the 
QgsVectorLayer::setReadOnly( bool readonly )" interface. So in case we would 
need that at the provider level (which is not so confirmed in this case) we 
could plug that there.

Side note: on a quick try there's some oddity in the GUI. If I just change a 
layer to Read-Only the "Toggle editing" button is still enabled. It becomes 
disabled only after I choose the "Select features by id" mode and clicked on a 
feature. And symetrically when changing back to Read-Write.

> 
> Nyall
> 
> > -------------------
> > 
> > This also leads to a follow up question: many OGR data formats have "open
> > options". As far as I know, these options are not exposed to the User in
> > QGIS, other than the encoding - or did I miss something? Should we
> > introduce a "GUI" way in QGIS 3.x to expose these "open options" in the
> > "add vector layer" dialogue?
> > 
> > Thanks,
> > Andreas
> > 
> > On 2016-10-01 23:38, Even Rouault wrote:
> > 
> > FYI: An interesting finding to improve performance of large Geopackage on
> > a shared network drive.
> > 
> > ----------  Message transmis  ----------
> > 
> > Sujet : Re: [Geopackage] Geopackage on a shared network drive
> > Date : samedi 01 octobre 2016, 16:41:05
> > De : Árni Geirsson via Geopackage <geopackage at lists.opengeospatial.org>
> > À : Even Rouault <even.rouault at spatialys.com>
> > CC : geopackage at lists.opengeospatial.org
> > 
> > Yes! It renders very quickly after I set the read-only flag in the file
> > explorer.
> > That goes a long way towards solving the problem for me because as I
> > mentioned, the team would like to use this format to store geodata, not
> > to edit it and certainly not to make edits by multiple concurrent users.
> > Thank you so much for your help!
> > 
> > Árni
> > 
> > 
> > Árni Geirsson
> > *Alta ehf* // +354 582 5000 // +354 897 9549
> > www.alta.is  // Alta á Twitter <http://twitter.com/alta_ehf> // Alta á
> > Facebook <http://www.facebook.com/pages/Alta/161795813838691?v=wall>
> > Gæða- og umhverfisstefna Alta <http://alta.is/pdf/svonavinnumvid.pdf>
> > 
> > 
> > 
> > 
> > On 1 October 2016 at 14:28, Even Rouault <even.rouault at spatialys.com>
> > wrote:
> > 
> > Le samedi 01 octobre 2016 16:02:38, Árni Geirsson a écrit :
> > 
> > Hello Even
> > Thank you for your suggestion. I made the changes you suggested, adding
> > set SQLITE_USE_OGR_VFS=YES
> > after
> > set VSI_CACHE=TRUE
> > set VSI_CACHE_SIZE=1000000
> > but there was no difference. Was this perhaps not the right way to do it?
> > 
> > 
> > Yes, that's correct.
> > 
> > Hum actually reviewing the code, the cache mechanism is only enabled when
> > the
> > file is opened in read-only mode, whereas QGIS will open the file in
> > read-write
> > mode.
> > 
> > You could perhaps try to make the GPKG read-only in the explorer?, at
> > least just to test if it is a promising optimization. I guess write
> > support for the
> > cache mechanism could be added.
> > 
> > A drawback of a cache machnism is that it would defeat the updates in
> > SQLite
> > to deal with concurrent editing, but anyway such mechanisms don't work
> > very well on network shares.
> > 
> > Anyway, I would think that I am not alone in seeing this as a problem
> > 
> > but I
> > 
> > find very little about it on the web.
> > 
> > Árni
> > 
> > 
> > 
> > Árni Geirsson
> > *Alta ehf* // +354 582 5000 // +354 897 9549
> > www.alta.is  // Alta á Twitter <http://twitter.com/alta_ehf> // Alta á
> > Facebook <http://www.facebook.com/pages/Alta/161795813838691?v=wall>
> > Gæða- og umhverfisstefna Alta <http://alta.is/pdf/svonavinnumvid.pdf>
> > 
> > 
> > 
> > 
> > On 30 September 2016 at 19:52, Even Rouault <even.rouault at spatialys.com>
> > 
> > wrote:
> > 
> > Le vendredi 30 septembre 2016 00:44:45, Árni Geirsson via Geopackage a
> > 
> > écrit :
> > 
> > Dear Geopackage developers!
> > I look forward to the day when Geopackage replaces the old shapefiles
> > 
> > 
> > and I
> > 
> > thank you for your efforts. As a user in a small team that uses QGIS
> > and shares data on a NAS box, basically a Samba server for network
> > shares, I notice that Geopackage data loads very slowly, much more
> > slowly than a shapefile stored in exactly the same shared folder. I
> > have noticed this with Spatialite, too, and suspect that the problem
> > lies with Sqlite and some problem it has with the networking
> > 
> > protocol.
> > 
> > Since Geopackage is intended (as I understand) as a storage and
> > exchange format for geodata, rather than a general purpose database
> > format like Spatialite, I was
> > 
> > 
> > hoping
> > 
> > that this problem could be overcome and that the Geopackage data
> > 
> > would
> > 
> > 
> > load
> > 
> > as fast as the shapefile data from the network share. When the
> > Geopackage and shapefile data are both on a local drive, I see no
> > difference in the loading speed.
> > 
> > Do you think this will be solved?
> > 
> > 
> > QGIS tweaks GDAL/OGR to use a large buffer size to speed up network
> > access to
> > shapefiles (or any format that uses the GDAL I/O layer, which is called
> > "VSI").
> > 
> > If you look at the qgis.bat in c:\osgeo4w\bin, you will see :
> > set VSI_CACHE=TRUE
> > set VSI_CACHE_SIZE=1000000
> > 
> > But by default, the OGR GPKG driver uses SQLite own I/O layer, which
> > probably
> > does access with a granualrity of a SQLite page size (4KBytes). You
> > 
> > could
> > 
> > tried to define the
> > SQLITE_USE_OGR_VFS=YES environmenet variable, restart QGIS and then
> > SQLite should use the GDAL/OGR I/O layer and hopefully benefit from the
> > buffering. I
> > have not tried that, so not completely sure if it will improve things.
> > 
> > Even
> > 
> > --
> > Spatialys - Geospatial professional services
> > http://www.spatialys.com
> > 
> > 
> > --
> > Spatialys - Geospatial professional services
> > http://www.spatialys.com
> > 
> > 
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> > 
> > 
> > 
> > 
> > 
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