Updated SQLite (markdown)
springmeyer
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SQLite.md
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SQLite.md
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<!-- Name: SQLite -->
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<!-- Version: 11 -->
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<!-- Last-Modified: 2010/11/13 10:07:41 -->
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<!-- Author: kunitoki -->
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Mapnik's PluginArchitecture supports the use of different input formats.
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One such plugin supports the sqlite ([SQLite](http://en.wikipedia.org/wiki/SQLite)) / spatialite ([Spatialite](http://www.gaia-gis.it/spatialite)) extension to the popular SQLite database.
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One such plugin supports the sqlite ([SQLite](http://en.wikipedia.org/wiki/SQLite)). The plugin works with two types of geometry storage methods - raw OGC WKB and ([Spatialite](http://www.gaia-gis.it/spatialite)) geometries.
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# Installation
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You can create a pure SQLite + WKB geometry based sqlite db using ogr like:
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Make sure that running _python scons/scons.py DEBUG=y_ shows the following line
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ogr2ogr -f SQLite test.sqlite some.shp
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Checking for C library sqlite3... yes
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You can create a spatialite enabled db also using ogr:
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To check if the sqlite plugin built and was installed correctly, try the usual Python _from mapnik import *_ on a DEBUG=y build, and look for the following debug line
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ogr2ogr -f SQLite test.sqlite some.shp -dsco SPATIALITE=YES
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registered datasource : sqlite
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# Creating an example database
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## Getting the tools
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First of all we need a bit of external tools for loading and preparing our first spatial database with sqlite.
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Go to [Spatialite](http://www.gaia-gis.it/spatialite-2.3/) and download (depending on your arch) the "spatialite executable [statically linked, no deps]" and unpack them in a directory of choice. Also download and unpack [InitSpatialiteSql](http://www.gaia-gis.it/spatialite/init_spatialite-2.2.sql.zip) in the same directory.
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If you have problems with your spatial indexes (mbr calculated wrong in tables idx_table_geometry), you will need to rebuild spatialite-2.3 yourself using a recent version of GEOS (>=3.0.3): refer to [Spatialite](http://www.gaia-gis.it/spatialite-2.3) compilation guide.
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## Prepare the data
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Now execute spatialite on a new empty database:
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user@geo ~/spatialite/ $ spatialite spatial_test.sqlite
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SpatiaLite version ..: 2.3 Supported Extensions:
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- 'VirtualShape' [direct Shapefile access]
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- 'VirtualText [direct CSV/TXT access]
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- 'VirtualNetwork [Dijkstra shortest path]
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- 'RTree' [Spatial Index - R*Tree]
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- 'MbrCache' [Spatial Index - MBR cache]
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- 'VirtualFDO' [FDO-OGR interoperability]
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- 'SpatiaLite' [Spatial SQL - OGC]
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PROJ.4 version ......: Rel. 4.6.1, 21 August 2008
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GEOS version ........: 3.0.0-CAPI-1.4.1
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SQLite version ......: 3.6.6.1
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Enter ".help" for instructions
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spatialite>
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From the spatialite shell you must initialize the spatialite tables (_geom_cols_ref_sys_, _geometry_columns_, _spatial_ref_sys_):
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spatialite> .read init_spatialite-2.2.sql ASCII
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1
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We import a shapefile directly inside our database (in this example using utf-8 encoding, 3004 as SRID(epsg) and 'geom' as the geometry column). This will take care of creating the table for us, executing *AddGeometryColumn* which will initialize the _geometry_columns_ table and add a BLOB column to our table for the geometry, then it will insert the rows into it:
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spatialite> .loadshp bridges bridges UTF-8 3004 geom
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========
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Loading shapefile at 'bridges' into SQLite table 'bridges'
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BEGIN;
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CREATE TABLE bridges (
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PK_UID INTEGER PRIMARY KEY AUTOINCREMENT,
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ANNO_COSTR INTEGER,
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RAG_GIUR INTEGER,
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DECORAZ TEXT);
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SELECT AddGeometryColumn('bridges', 'geom', 3004, 'MULTIPOLYGON', 2);
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INSERT INTO ponte (
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PK_UID,ANNO_COSTR,RAG_GIUR,DECORAZ,geom)
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VALUES (1,0,1,'',GeomFromWkb(X'010600000001000000010300000001000000150000001A...',3004));
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...
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COMMIT;
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Inserted 499 rows into 'bridges' from SHAPEFILE
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========
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At this point we can decide also to create the R*Tree index on this table, for speed spatial access to the table:
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spatialite> select CreateSpatialIndex('bridges', 'geom');
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1
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You can now exit the spatialite shell:
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spatialite> .quit
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The main difference is that a spatialite enabled db will include a spatial index inside the database. A pure SQLite db will not contain a spatial index, but Mapnik will create one on the fly.
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# Parameters
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@ -129,4 +61,4 @@ A Sqlite datasource may be created as follows:
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}
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```
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## Further References
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## Further References
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