[gdal-dev] Problem using gdalbuildvrt with a large number of source datasets

[Homme Zwaagstra]

Hello,

I've come up against a problem with `gdalbuildvrt` taking a long time to 
create
a VRT when it is passed a large number of source datasets. I am trying 
to create
a VRT file for a zoom level in a TMS structure containing JPEG tiles.  The
command I'm using is:

gdalbuildvrt output.vrt `find ./tiles/18 -iname *.jpg -printf "%p "`

where the number of tiles is:

$ find ./tiles/18 -iname *.jpg | wc -l
767104

The processing seemed to progress reasonably quickly with the progress bar
outputing '0... etc ...100 - done'.  However `gdalbuildvrt` continued 
running
until I killed it 8 hours later.  Looking at `output.vrt` just before I 
killed
the program showed it remained empty (0 bytes).

Before digging any deeper is there something I'm missing? Am I expecting too
much of `gdalbuildvrt`, or indeed the VRT format, in processing this 
many source
datasets?

Conceptually in this instance it seems as if it would be useful for a 
VRT file
(and `gdalbuildvrt`) to reference the output of `gdaltindex` or something
similar.  I'm not sure how efficiently source datasets are indexed in 
VRTs and
whether this might be contributing to the problem?

Best regards,

Homme Zwaagstra