[postgis-users] Qgis + PostGis. Low operating speed.

[Regina Obe]

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:postgis-users-bounces at lists.osgeo.org] On Behalf Of Alex German
Sent: Tuesday, December 13, 2022 4:12 AM
To: PostGIS Users Discussion <postgis-users at lists.osgeo.org>
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 <gr1047 at gmail.com <mailto:gr1047 at gmail.com> >:



SRID in postgis 4326



SRID in QGis 4326

 

 

вт, 13 дек. 2022 г. в 12:05, Bo Victor Thomsen <bo.victor.thomsen at gmail.com <mailto:bo.victor.thomsen at gmail.com> >:

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 <lr at pcorp.us <mailto:lr at pcorp.us> >:

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:postgis-users-bounces at lists.osgeo.org <mailto:postgis-users-bounces at lists.osgeo.org> ] On Behalf Of Alex German
Sent: Monday, December 12, 2022 11:34 PM
To: PostGIS Users Discussion <postgis-users at lists.osgeo.org <mailto:postgis-users at lists.osgeo.org> >
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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Алексей Герман

8-905-86-00-416




 

-- 

Алексей Герман

8-905-86-00-416

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