Note: starting with GDAL 1.10, the driver is compiled only if GDAL is built with SQLite support.
Points are represented as wkbPoints, lines and boundaries as wkbLineStrings and areas as wkbPolygons. wkbMulti* features are not used. Feature types cannot be mixed in one layer.
Starting with GDAL 1.9, the driver uses SQLite as a backend database when reading VFK data. By default, SQLite database is created in a directory of input VFK file (with file extension '.db'). Since GDAL 1.10, the user can define DB name with OGR_VFK_DB_NAME configuration option. If OGR_VFK_DB_OVERWRITE=YES configuration option is given, the driver overwrites existing SQLite database and stores data read from input VFK file into newly created DB. Since GDAL 1.11, if OGR_VFK_DB_DELETE=YES configuration option is given, the driver deletes backend SQLite database when closing the datasource.
Starting with GDAL 1.10, resolved geometries are stored also in backend SQLite database. It means that geometries are resolved only once when building SQLite database from VFK data. Geometries are stored in WKB format. Note that GDAL doesn't need to be built with SpatiaLite support. Geometries are not stored in DB when OGR_VFK_DB_SPATIAL=NO configuration option is given. In this case geometries are resolved when reading data from DB on the fly.
Since GDAL 1.11, the driver reads by default all data blocks from VFK file when building backend SQLite database. When configuration option OGR_VFK_DB_READ_ALL_BLOCKS=NO is given, the driver reads only data blocks which are requested by the user. This can be useful when the user want to process only part of VFK data.
The driver supports reading files managed by VSI Virtual File System API, which include "regular" files, as well as files in the /vsizip/, /vsigzip/, and /vsicurl/ read-only domains.
Since GDAL 2.2 also a full path to the backend SQLite database can be used as an datasource. By default, such datasource is read by SQLite driver. If configuration option OGR_VFK_DB_READ=YES is given, such datasource is open by VFK driver instead.