[gdal-dev] SQLite dialect with GeoPackage

[Even Rouault]

Le lundi 06 octobre 2014 20:48:02, Stefan Ziegler a écrit :
> Hi Even
> 
> thanks! INDIRECT_SQLITE works like a charm. I could not figure out the
> syntax to create a new layer in the very same gpkg file:
> 
> stefan at hatschepsut:~/Downloads$ ogr2ogr -append -f GPKG 2601.gpkg -nln
> my_new_layer -dialect INDIRECT_SQLITE -sql 'SELECT * FROM
> bodenbedeckung__bbtext WHERE tid IN (SELECT tid FROM bodenbedeckung__bbtext
> GROUP BY ST_X(ST_SnapToGrid(geom, 500)), ST_Y(ST_SnapToGrid(geom, 500)),
> nummer_name ORDER BY ST_X(ST_SnapToGrid(geom,500)),
> ST_Y(ST_SnapToGrid(geom, 500)), ST_Distance(geom, ST_SnapToGrid(geom,
> 500)))' 2601.gpkg
> ERROR 1: sqlite3_exec(CREATE TABLE "my_new_layer" ( "fid" INTEGER PRIMARY
> KEY AUTOINCREMENT, "geom" POINT )) failed: database is locked
> ERROR 1: Terminating translation prematurely after failed
> translation from sql statement.
> 
> Is this even possible?

Ah, good point. I've just added a particular case in ogr2ogr, like done for 
sqlite, when input dataset = output dataset, to open the database just once to 
avoid that locking issue.

> 
> regards
> Stefan
> 
> 
> On Mon, Oct 6, 2014 at 8:20 PM, Even Rouault <even.rouault at spatialys.com>
> 
> wrote:
> > Le lundi 06 octobre 2014 19:41:43, Stefan Ziegler a écrit :
> > > Hi
> > > 
> > > When trying to use SQLite dialect with GeoPackage I get some errors,
> > 
> > like:
> > > stefan at hatschepsut:~/Downloads$ ogrinfo -al -sql 'SELECT
> > > ST_X(ST_SnapToGrid(geom,1)) FROM bodenbedeckung__bbtext LIMIT 1'
> > > 2601.gpkgINFO: Open of `2601.gpkg'
> > > 
> > >       using driver `GPKG' successful.
> > > 
> > > ERROR 1: In ExecuteSQL(): sqlite3_prepare(SELECT
> > > 
> > > ST_X(ST_SnapToGrid(geom,1)) FROM bodenbedeckung__bbtext LIMIT 1):
> > >   no such function: ST_SnapToGrid
> > > 
> > > The same query works with Shapefiles. I thought the SQLite dialect can
> > > be used with any OGR datasource?
> > 
> > Stefan,
> > 
> > You need a very recent Spatialite (4.2 I think) for compatibility with
> > GeoPackage. But your request would not work since Spatialite functions
> > can only work with Spatialite geometry blobs and not Geopackage geometry
> > blobs. Spatialite 4.2 provide explicit conversion methods AsGPB /
> > GeomFromGPB.
> > 
> > For example :
> > 
> > $ ogrinfo poly.gpkg -sql "select
> > AsGPB(ST_SnapToGrid(GeomFromGPB(geom),1)) from poly"
> > 
> > I've also just added in trunk a "INDIRECT_SQLITE" dialect that will cause
> > the
> > generic solution used for shapefiles for example to be usable by
> > GeoPackage datasources too. But this will be slower than direct SQL due
> > to an extra translation layer done by OGR ( GPKG -> OGR feature ->
> > SQLite/Spatialite virtual table -> OGR feature ).
> > 
> > $ ogrinfo poly.gpkg -sql "select ST_SnapToGrid(geom,1) from poly"
> > -dialect INDIRECT_SQLITE
> > 
> > Even
> > 
> > --
> > Spatialys - Geospatial professional services
> > http://www.spatialys.com

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