postGIS vs. TAB files

[Frank Warmerdam]

On 8/5/05, Richard Greenwood <richard.greenwood at gmail.com> wrote:
> Bart van den Eijnden <BEN <at> SYNCERA-ITSOLUTIONS.NL> writes:
> 
> >
> > One problem of the TAB support through OGR currently is that the attribute
> indexes are not being used. So
> > doing queries on large TAB files is not that fast.
> >
> > Best regards,
> > Bart
> 
> With shape files you can create an attribute index with OGR:
>   ogrinfo -ro myTable -sql "create index on listing using ID"
> This creates an XML file which tells OGR that there is an
> attribute index, and a MapInfo format index (so you might
> want to drop MapInfo indexes before you creat the new index).
> 
> I do not know if this works with TAB files.

Rich,

Unfortunately, OGR does not use mapinfo attribute indexes
for mapinfo format, even though it uses them for shapefiles.  I would
add that currently these indexes are only useful for unique value
lookup.   They don't help for ranges, or non-unique values. 
So, as mentioned, PostGIS does offer alot of flexibility and speed
for different kinds of attribute queries that OGR's TAB support lacks.

I would note that OGR's Mapinfo driver does support spatial indexes,
so PostGIS shouldn't have a significant advantage on that front. 

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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