[gdal-dev] AVCBin driver really slow on e00 data

[Frank Warmerdam]

Ari Jolma wrote:
> I have a fairly large (43MB) e00 ascii data file. ogrinfo spends a 
> couple of minutes to report that it contains ARC, CNT, LAB, PAL and RPL 
> layers. The command
> 
> ogrinfo x.e00 PAL
> 
> opens the file and reports eventually that there are a certain number of 
> features and then seems to take forever. PAL is a polygon feature class. 
> ogrinfo on LAB points works much faster.
> 
> Why is it so time consuming to look into polygon features inside e00?

Ari,

In order to read the PAL layer, the reader spends a great deal of time
seeking around in the file collecting the nodes and arcs in order to form
them into a polygon geometry for each feature.

I think you will see better performance if you first convert the e00 file
into a binary coverage with the avcimport utility.  The performance of the
OGR E00 driver is really not acceptable for large polygon files.

I would also note there have been reports that the polygons are not always
properly reconstructed, so the results may not even be right when directly
accessing the e00 files.

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