[gdal-dev] DBF indexing?

[Smith, Michael ERDC-CRREL-NH]

CREATE INDEX

Some OGR SQL drivers support creating of attribute indexes. Currently this
includes the Shapefile driver. An index accelerates very simple attribute
queries of the form fieldname = value, which is what is used by the JOIN
capability. To create an attribute index on the nation_id field of the
nation table a command like this would be used:
CREATE INDEX ON nation USING nation_id

Index Limitations
1. Indexes are not maintained dynamically when new features are added to
or removed from a layer.
2. Very long strings (longer than 256 characters?) cannot currently be
indexed.
3. To recreate an index it is necessary to drop all indexes on a layer and
then recreate all the indexes.
4. Indexes are not used in any complex queries. Currently the only query
the will accelerate is a simple "field = value" query.


http://gdal.org/ogr/ogr_sql.html






On 4/25/12 8:38 PM, "William Kyngesburye" <woklist at kyngchaos.com> wrote:

>Is it possible to index fields in a DBF, and does GDAL support that for a
>JOIN?
>
>-----
>William Kyngesburye <kyngchaos*at*kyngchaos*dot*com>
>http://www.kyngchaos.com/
>
>"Those people who most want to rule people are, ipso-facto, those least
>suited to do it."
>
>- A rule of the universe, from the HitchHiker's Guide to the Galaxy
>
>
>_______________________________________________
>gdal-dev mailing list
>gdal-dev at lists.osgeo.org
>http://lists.osgeo.org/mailman/listinfo/gdal-dev