[gdal-dev] Questions regarding temporary database file (ogr2ogr with MVT driver)

[leo.fuhrmann.lgln at icloud.com]

Hi,

I’m creating vector tiles from a PostGIS database using ogr2ogr with the MVT driver. The region is quite large and I’m creating tiles for levels 0-15, so the process takes quite some time (hours). The tiles are written directly to a S3 storage using the /vsis3/ virtual file system (see: https://gdal.org/user/virtual_file_systems.html#vsis3-aws-s3-files).

Looking at the logs, I can see that, firstly, a “temporary database” file (*.temp.db) is created. Some things are notable:

- this step seems to be CPU intensive compared to the creation of the actual pbf files
- the temporary database file is not being written to the output file directory (S3 storage in this case) as stated in the documentation
- the dataset creation option `TEMPORARY_DB` (see: https://gdal.org/drivers/vector/mvt.html#dataset-creation-options) seems to be ignored (I tried writing the file to a local directory but no such file shows up)
- my guess is that the file is only kept in memory (which would be /vsimem/ if I’m correct)

Is it possible to skip the step of first creating the temp db and directly create tiles from PostGIS or any other data source? Where/how exactly is the database file stored? Any ideas on optimizing the process?

I’m looking forward to some discussion on this topic. I will happily try to contribute where I can.

Regards,

Leo
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