[gdal-dev] Add a new performance hint for Spatialite

[Rahkonen Jukka (Tike)]

Hi,

Sorry, I must have not emphasized enough that hint is only valid for appending data with subsequent ogr2ogr commands

ogr2ogr -f sqlite -dsco spatialite=yes mtk_tos.sqlite -dim 2 -lco spatial_index=no /vsizip/e:\mtk_tos\etrs89\gml\K32.zip tieviiva  -gt 65536
ogr2ogr -f sqlite -append mtk_tos.sqlite -dim 2 /vsizip/e:\mtk_tos\etrs89\gml\K34.zip tieviiva -gt 65536
... repeat the latter command for 113 more GML files...

I am not sure if this is a common use case everywhere. However, our National Land Survey delivers vector data divided by map sheets which means that each country wide dataset contains hundreds or thousands of GML files.
 
Even Rouault wrote:
 
> Jukka,
> 
> I'm very surprised that you need to do that explicitely, since the driver should
> already do that by default. This is something we discovered last year or the year
> before when you were experimenting OSM -> Spatialite conversions. Since OGR
> 1.10, the spatial index is created when the datasource is closed.
> 
> Look at this debug trace:
> 
> $ ogr2ogr -f sqlite /vsimem/out.sqlite ../autotest/ogr/data/poly.shp -dsco
> spatialite=yes --debug on
> OGR: OGROpen(../autotest/ogr/data/poly.shp/0x69a3d0) succeeded as ESRI
> Shapefile.
> SQLITE: SpatiaLite v4 DB found !
> OGR_SQLITE: exec(CREATE TABLE 'poly' (   OGC_FID INTEGER PRIMARY KEY))
> OGR_SQLITE: exec(DELETE FROM geometry_columns WHERE f_table_name =
> 'poly')
> OGR_SQLITE: exec(SELECT AddGeometryColumn('poly', 'GEOMETRY', 325834,
> 'POLYGON',
> 2))
> OGR_SQLITE: exec(ALTER TABLE 'poly' ADD COLUMN 'area' FLOAT)
> OGR_SQLITE: exec(ALTER TABLE 'poly' ADD COLUMN 'eas_id' FLOAT)
> OGR_SQLITE: exec(ALTER TABLE 'poly' ADD COLUMN 'prfedea' VARCHAR(16))
> OGR_SQLITE: BEGIN Transaction
> OGR_SQLITE: prepare(INSERT INTO 'poly'
> ("GEOMETRY","area","eas_id","prfedea")
> VALUES (?,?,?,?))
> OGR_SQLITE: COMMIT Transaction
> OGR2OGR: 10 features written in layer 'poly'
> OGR_SQLITE: exec(SELECT CreateSpatialIndex('poly', 'GEOMETRY'))
> SQLITE: Error no such table: layer_statistics
> OGR: Unloading VirtualOGR module
> Shape: 10 features read on layer 'poly'.
> 
> Could try adding --debug on to your ogr2ogr command line and see when
> CreateSpatialIndex() is created ?
> 
> Even
> 
> > Hi,
> >
> > I took timings about adding 115 GML files (548 MB together, 3.2
> > million
> > linestrings) into a Spatialite table. With default settings the table
> > gets initialized with spatial index which makes following inserts
> > slower. Another alternative is to create the table without spatial
> > index, append all the data first and as a last step create spatial index for the
> ready made table.
> >
> > With spatial index on:
> > Append + index: 71 minutes
> >
> > With spatial index off:
> > Append: 9 minutes
> > Create spatial index: 6 minutes
> > Total: 15 minutes
> >
> > I was rather happy with the initial conversion speed until I made this
> > test which revealed that creating spatial index as a final step made
> > the whole process more than four times faster! This way both data
> > table and spatial index are probably in contiguous chunks in the
> > SQLite datafile and there is no need for post process VACUUM.
> > Vacuuming in SQLite is rather slow and for this 1.3 GB database it takes more
> than 4 minutes to run.
> >
> > Suggestion: Add a new performance hint on page
> > http://www.gdal.org/ogr/drv_sqlite.html
> >
> > "If many source files will be collected into the same Spatialite table
> > it can be much faster to initialize the table without a spatial index
> > by using -lco SPATIAL_INDEX=NO and to create spatial index with a
> > separate command after all the data are appended. Spatial index can be
> > created with ogrinfo command ogrinfo db.sqlite -sql "SELECT
> > CreateSpatialIndex('table_name','geometry_column_name')"
> >
> > Perhaps it could also be mentioned as a performance hint that VACUUUM
> > can also be done from orginfo as ogrinfo db.sqlite -sql "VACUUM"
> >
> > -Jukka Rahkonen-
> >
> >
> >
> > _______________________________________________
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> > http://lists.osgeo.org/mailman/listinfo/gdal-dev
> >
>