There are any number of dbf indexes around; just no standard one I can think of
(I think ndx was the origional?)
As an example ArcGIS 8 has a atx file which is an attribute index[1].
If you would like to write an attribute index; or even hold an attribute index
in memory; we would welcome the code contribution.
Jody
[1] http://en.wikipedia.org/wiki/Shapefile
On 29/09/2010, at 10:13 PM, Andrea Aime wrote:
> On Wed, Sep 29, 2010 at 9:08 AM, LSA <[email protected]> wrote:
> Hi all!
>
> I need to perform quick search on dbf, i.e. find specific record by some
> attribute. I am thinking about using ODBC via JDBC, because
> 1) it can be used like this:
> Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
> String url = “jdbc:odbc:Driver={Microsoft dBase Driver
> (*.dbf)};DBQ=d:/shapefiles”;
> Connection con = DriverManager.getConnection(url);
> Statement st = con.createStatement();
> ResultSet rs = st.executeQuery(“SELECT * FROM countries where name='Homeland'
> ”);
> st.executeUpdate(“CREATE TABLE NEWTABLE (NAME CHAR(32), PASSWD CHAR(32))”);
> con.close(); 2) I don`t know, by I believe it can create index on specific
> field, so search will be about log2(n) time (n is recordCount).
>
> That would be news to me. DBF does not define a standard attribute indexing
> scheme. Maybe some drivers add custom indexes.
>
> 3) Default geotools data access is slow, unfortunately. Besides, it cannot
> use attribute index on dbf, as far as I know.
>
>
> Not supported as far as I know.
>
> So, the question: Does anybody ever performed fast searches on DBFs?
> What did you used, if so?
>
> I'd suggest to load the data in to a fast embedded database such as H2 or
> HSQL, if you have to do many repeated searches that will quickly pay off.
>
> If ODBC is a good choice? In future we will port our app to unixes, will we
> have dbf odbc there?
>
> Unlikely, but I may be wrong.
>
> Cheers
> Andrea
>
> -----------------------------------------------------
> Ing. Andrea Aime
> Senior Software Engineer
>
> GeoSolutions S.A.S.
> Via Poggio alle Viti 1187
> 55054 Massarosa (LU)
> Italy
>
> phone: +39 0584962313
> fax: +39 0584962313
>
> http://www.geo-solutions.it
> http://geo-solutions.blogspot.com/
> http://www.linkedin.com/in/andreaaime
> http://twitter.com/geowolf
>
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