[postgis-users] GDAL OUT-DB RASTER SUPPORT

Osahon Oduware osahon.gis at gmail.com
Wed May 3 09:02:21 PDT 2017


Hi Regina,

I followed the process you described to create a view for the out-db
rasters and dragged it to the map. I was able to view the out-db rasters
this way. However, *it takes very long before the raster is displayed on
the map* (in QGIS) as compared to the time taken to display an in-db raster.

Is there anything that can be done to improve the speed?


NB: indexes were created with the -I flag of the raster2pgsql tool

On Fri, Apr 28, 2017 at 4:07 PM, Regina Obe <lr at pcorp.us> wrote:

> 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 J├╝rgen 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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