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Huge Performance Regression using VRTs on Versions > 3.40.6 #63293

Description

@bedaberner

What is the bug or the crash?

I use midsized VRTs made from ARGB Geotiff tiles ( in the example I look at, 290 tiles 5000x5000 pixels, total of 27gb).

I used version 3.40.6 so far and Everything works as expected. Opening the VRT takes 1-2 seconds on my very powerful machine (Ryzen 9950x, 128gb Ram, RTX4090). After opening the file, upon zooming in, there is a pixalated "preview" but it loads better resolution data very quickly.

I wanted to update to the newest LTR release (3.40.10 at the time but i have since tried 3.40.11 and 3.44.2 as well and they all behave the same.)

In these Versions opening the VRT takes forever (multiple minutes) and once it is loaded, only the very low resolution preview is available. Upon zooming in, no higher resolution data is loaded (or maybe it would after more than 5 min but i didn't wait that long.)

Steps to reproduce the issue

I have created an example dataset which is very similar to mine, however I replaced all RGB Values with 1,1,1 both for compression and privacy reasons. It does however still display the same behavior as the RGB Variant. Opening this in 3.40.11 will take forever, in 3.40.6 it's almost instant.

test_VRT.zip (This might require 7zip to open)

Versions

3.40.11 LTR with slow loading:

QGIS-Version3.40.11-Bratislava
QGIS-Codeversiondf059ed19c
 
Bibliotheken
Qt-Version5.15.13
Python-Version3.12.11
GDAL-Version3.11.3 — Eganville
PROJ-Version9.6.2
EPSG-Registraturdatenbankversionv12.013 (2025-05-26)
GEOS-Version3.13.1-CAPI-1.19.2
SQLite-Version3.50.4
PDAL-Version2.9.0
PostgreSQL-Client-Versionunknown
SpatiaLite-Version5.1.0
QWT-Version6.3.0
QScintilla2-Version2.14.1
BS-VersionWindows 11 Version 2009
 
Aktive Python-Erweiterungen
db_manager0.1.20
grassprovider2.12.99
MetaSearch0.3.6
processing2.12.99

3.40.6, Version that works well:

QGIS-Version3.40.6-Bratislava
QGIS-Codeversion5d7f6a3e26
 
Bibliotheken
Qt-Version5.15.13
Python-Version3.12.10
GDAL-Version3.10.3
PROJ-Version9.6.0
EPSG-Registraturdatenbankversionv12.004 (2025-03-02)
GEOS-Version3.13.1-CAPI-1.19.2
SQLite-Version3.46.1
PDAL-Version2.8.3
PostgreSQL-Client-Versionunknown
SpatiaLite-Version5.1.0
QWT-Version6.3.0
QScintilla2-Version2.14.1
BS-VersionWindows 11 Version 2009
 
Aktive Python-Erweiterungen
contour2.0.15
MemoryLayerSaver6.0.0
quick-geojson1.0
db_manager0.1.20
MetaSearch0.3.6
processing2.12.99

Supported QGIS version

  • I'm running a supported QGIS version according to the roadmap.

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BugEither a bug report, or a bug fix. Let's hope for the latter!RastersRelated to general raster layer handling (not specific data formats)RegressionSomething which used to work, but doesn't anymoreUpstreamNeeds changes in an upstream library (like Qt, Proj, GDAL, ...)

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