[Qgis-developer] Geospackage Slow in QGIS
JPalmer at linz.govt.nz
Sat May 17 13:14:54 PDT 2014
Thanks for the change! I've now tested the GDAL trunk with QGIS and it's lightning fast with large files - problem solved.
Thanks once again,
From: Even Rouault [even.rouault at mines-paris.org]
Sent: Saturday, 17 May 2014 10:48 p.m.
To: qgis-developer at lists.osgeo.org
Cc: Stefan Keller; Jeremy Palmer
Subject: Re: [Qgis-developer] Geospackage Slow in QGIS
Le samedi 17 mai 2014 10:46:39, Stefan Keller a écrit :
> So it's this code fragment?
> 419 /* Requirement 6: The SQLite PRAGMA integrity_check SQL command
> SHALL return â??okâ? */
> 420 /* http://opengis.github.io/geopackage/#_file_integrity */
> 421 if( strncmp(pszFilename, "/vsicurl/", strlen("/vsicurl/")) != 0 &&
> 422 OGRERR_NONE != PragmaCheck("integrity_check", "ok", 1) )
> Looks strange to me why a single file check woold be the bottlenet since
> this should be a single call.
> I would have expected that some repeated calls (like reading
> objects/records and checking SRID or data types) would be the bottleneck
> since SQlite is not performant when used with PRAGMA checks. This would be
> a check one could disable with a parameter.
I've just noticed that thread. Actually I found that integrity_check was slow
when operating on remote databases with /vsicurl/ and didn't verify how slow
it could be with local big files, but its documentation at
http://www.sqlite.org/pragma.html#pragma_integrity_check suggests that it
might be bery slow indeed.
Reading the GeoPackage spec, nothing mandates to do the integrity_check at
open time. It only mandates that if you run "pragma integrity_check" it should
retrun OK. So I've disabled the check by default.
Geospatial professional services
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