Fix speed regression in paletted raster renderer #56677
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Don't try to condense classes if we have many classes, it's too slow to do and results in many-minute hangs in the UI for large class counts Fixes qgis#56652
nyalldawson
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backport release-3_36
backport queued_ltr_backports
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It looks like the issue fixed with this PR also makes QGIS hang for a very long time when importing paletted GeoTIFF layers (e.g. the output layers of some GRASS-GIS processing algorithms). |
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@nyalldawson TBH I really don't like this band-aid. Let me see if I can find a better fix. |
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@nyalldawson see: #56784 |
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Don't try to condense classes if we have many classes, it's too slow to do and results in many-minute hangs in the UI for large class counts
Fixes #56652
This is a bit of a quick-and-nasty fix -- possibly we could fix the issue in a better way with a hash lookup, but I couldn't get that working without still incurring a multi-second hang. I'm not sure what the real-world consequences are for NOT condensing classes here.
@elpaso do you have any insights? This was introduced as part of the raster attribute table work.