[postgis-users] GDAL OUT-DB RASTER SUPPORT

[Regina Obe]

Osahon,

 

It depends what you are trying to show and do.

 

1)      For example if you create overviews on your out-db, those will show, so then it would only be when you zoom in that you hit the out-db that you'd get black.

 

2)      If you are looking to inspect a slice of out-db with QGIS, you can create a view that has just the piece you want to show and drag it to your map.

You'd need to apply a function that forces that piece into in-db.  Not all raster functions do that and sadly we haven't been good about documenting ones that do vs. ones that don't.

 

I know for sure that ST_Resize would force a materialized in-db and that might actually be a good one to use anyway since it would lower the res allowing you to see more.

 

 

So something like

-- do this with db manager or pgAdmin

 

CREATE OR REPLACE VIEW vw_outdb_sample AS

SELECT rid, ST_Resize(rast,0.8, 0.8) AS rast

FROM some_outdb_table

WHERE ST_Intersects(rast,some_geometry);

 

 

Then drag this view to your Map.

 

 

Hope that helps,

Regina

 

 

From: Osahon Oduware [mailto:osahon.gis at gmail.com] 
Sent: Friday, April 28, 2017 10:13 AM
To: PostGIS Users Discussion <postgis-users at lists.osgeo.org>
Cc: Regina Obe <lr at pcorp.us>; pierre.racine at sbf.ulaval.ca
Subject: GDAL OUT-DB RASTER SUPPORT

 

Hi All,

I am getting a black image when I try to display PostGIS out-db rasters. I discovered that it has to do with GDAL support for out-db rasters as stated in the link below for a similar issue (over 1 year back):
https://hub.qgis.org/issues/12133

The last comment by Jürgen Fischer states "... only black images. So it's a dependency issue (GDAL complains ERROR 1: This raster has outdb storage. This feature isn't still available)."

I have also been told in the link below that "out-db support is not implemented yet in the GDAL PostGISRaster driver.":
https://lists.osgeo.org/pipermail/gdal-dev/2017-April/046512.html

I would like to know how to solve this issue of displaying postgis out-db rasters in QGIS?

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