[postgis-users] st_createoverview

[Sandro Santilli]

On Thu, Apr 14, 2016 at 10:39:53AM +0200, Horst Düster wrote:
> Thanks for your response.
> 
> I created a workflow how to reproduce the mentioned behaviour:
> 
> 1. Upload the image clean_tiled.tif to my DB with:
> raster2pgsql -t auto -I -f rast clean_tiled.tif | pgsql .....
> 
> (Upload file clean_tiled.sql is attached)
> 
> 2. Create overviews for levels 2,4,8,16,32 with
> 
> select st_createoverview('clean_tiled'::regclass, 'rast'::name, 2) etc.
> 
> 3. Load DB raster to QGIS with DB manager or have a look at [1] to get
> the result.

I confirm that the ST_Union of all the tiles from the overview created
with ST_CreateOverviews(..., 2) contains gaps which are not present in
the union of the original table.

Note that ST_CreateOverviews is a wrapper around ST_Retile:
http://postgis.net/docs/manual-2.2/RT_Retile.html

It would be useful to check if calling ST_Retile against the *union*
of the input raster tiles would change things.

--strk;