That’s a bummer.  You know how long that has been?  I recall it working when 
postgis raster access from QGIS was more or less a straight connection to GDAL. 
 I think that changed in the past 2-3 years or so.

 

From: postgis-users [mailto:[email protected]] On Behalf Of 
Alex German
Sent: Wednesday, December 14, 2022 1:36 AM
To: PostGIS Users Discussion <[email protected]>
Subject: Re: [postgis-users] Qgis + PostGis. Low operating speed.

 

Thanks, Regina! On the Qgis forum, I was told that overviews from PostGIS to 
Qgis do not work.

 

ср, 14 дек. 2022 г. в 09:02, Regina Obe <[email protected] <mailto:[email protected]> >:

That comes as a big surprise to me. It’s been a while since I’ve used QGIS on 
raster, but last time I tried it was able to read the overview tables.

 

I know there was a time not too long ago when QGIS was revising how it queries 
PostGIS raster. I forget what that revision was about, if it was just changing 
how it used GDAL to query PostGIS or getting rid of GDAL in some cases.

So this might have caused an issue with its reading of overviews.

 

I’ll try to test this out with latest QGIS in sometime this or next week to 
verify what the issue is here.

 

Thanks,

Regina

 

 

 

From: postgis-users [mailto:[email protected] 
<mailto:[email protected]> ] On Behalf Of Alex German
Sent: Tuesday, December 13, 2022 4:12 AM
To: PostGIS Users Discussion <[email protected] 
<mailto:[email protected]> >
Subject: Re: [postgis-users] Qgis + PostGis. Low operating speed.

 

QGis does not pick up overviews. 

Separately, overviews are loaded very quickly. 

I.e. if I load o_16_t6 in qgis, then the download speed is excellent. 

In the properties of the table, there are overviews.

 

вт, 13 дек. 2022 г. в 12:29, Alex German <[email protected] 
<mailto:[email protected]> >:



SRID in postgis 4326



SRID in QGis 4326

 

 

вт, 13 дек. 2022 г. в 12:05, Bo Victor Thomsen <[email protected] 
<mailto:[email protected]> >:

Is the rasters in same projection (CRS) as the QGIS project ? 

Med venlig hilsen / Best regards
 
Bo Victor Thomsen

Den 13-12-2022 kl. 07:50 skrev Alex German:

I did everything as described in the documentation. 

raster2pgsql -I -C -e -Y -F -s 4326 -t 128x128 -l 2,4,8,16,32 "d:\Temp\060 
tiff\res\t1.tif" testrastr.t1 | psql. 

The download is very slow.

https://youtu.be/LULngZIs4nc 

 

вт, 13 дек. 2022 г. в 09:45, Regina Obe <[email protected] <mailto:[email protected]> >:

PostGIS raster sadly doesn’t use the pyramids in the Tifs.  Or if it does no 
one told me.

 

You should build raster overviews using the raster2pgsql –l switch. 

https://postgis.net/docs/using_raster_dataman.html#RT_Raster_Loader

 

Doc example is this which builds a level 2 and 4 pyramid
raster2pgsql -I -C -e -Y -F -s 26986 -t 128x128  -l 2,4 bostonaerials2008/*.jpg 
aerials.boston | psql -U postgres -d gisdb -h localhost -p 5432

 

QGIS knows how to use the overviews built that way and should be much faster to 
view in QGIS

 

raster2pgsql -s 4326 -t 256x256 -C -I -F "d:\Temp\060 tiff\res\OCG_t1.tif" 
OCG_t1 -R| psql. 

 

 

From: postgis-users [mailto:[email protected] 
<mailto:[email protected]> ] On Behalf Of Alex German
Sent: Monday, December 12, 2022 11:34 PM
To: PostGIS Users Discussion <[email protected] 
<mailto:[email protected]> >
Subject: [postgis-users] Qgis + PostGis. Low operating speed.

 

Hello everyone!

I have a GeoTIFF. 

I built the pyramids in an external file using GDAL 

"gdaladdo d:\Temp\060 tiff\res\t1.tif -r lanczos -ro 2 4 8 16 32 64 128 256 
512. 

Uploaded to PostGIS using 

raster2pgsql -s 4326 -t 256x256 -C -I -F "d:\Temp\060 tiff\res\OCG_t1.tif" 
OCG_t1 -R| psql. 

The number of files is more than 1000. 

When trying to load tables in QGis, the loading is very slow. 

At the same time, downloading to QGis from files is fast. Question. What is not 
configured correctly and how to speed up the download to Qgis from PostGIS?


 

-- 

Alex German

 

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-- 

Алексей Герман 

8-905-86-00-416

 

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8-905-86-00-416




 

-- 

Алексей Герман

8-905-86-00-416

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-- 

Алексей Герман

8-905-86-00-416

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