<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><a href="https://trac.osgeo.org/postgis/ticket/5854">https://trac.osgeo.org/postgis/ticket/5854</a><br id="lineBreakAtBeginningOfMessage"><div><br><blockquote type="cite"><div>On Feb 24, 2025, at 10:22 AM, Paul Ramsey <pramsey@cleverelephant.ca> wrote:</div><br class="Apple-interchange-newline"><div><div>Replicated. I had to go up to 430 to make mine flip behaviour, but it is similar.<br><br>P.<br><br><blockquote type="cite">On Feb 24, 2025, at 9:46 AM, Frank Gevaerts <frank.gevaerts@fks.be> wrote:<br><br>Ok, I managed to simplify this to basically the example in the documentation:<br><br>This works fine, in a reasonable (typically 100ms to 150ms) time:<br>SELECT ST_Rotation(ST_Reskew(ST_AddBand(ST_MakeEmptyRaster(100, 359, 0, 0, 0.001, -0.001, 0, 0, 4269), '8BUI'::text, 1, 0), 0.0015));<br><br>This does not work fine, I stopped it after more than five minutes:<br>SELECT ST_Rotation(ST_Reskew(ST_AddBand(ST_MakeEmptyRaster(100, 360, 0, 0, 0.001, -0.001, 0, 0, 4269), '8BUI'::text, 1, 0), 0.0015));<br><br>The only difference is the size of the raster, the broken one having just one more row. The postgres process was using 100% CPU during that time, I don't think it was doing any IO (so no tempfiles as far as I could see).<br><br>I reproduced it on two systems, and things break for the same numbers, both on debian with postgresql 16, one with postgis 3.5.2/gdal 3.10.2, and one with postgis 3.4.2/gdal 3.2.2<br><br>Frank<br><br>On Mon, Feb 24, 2025 at 07:49:07AM -0800, Paul Ramsey wrote:<br><blockquote type="cite">If you provide a dump of a “good” raster, and a “bad” raster, and the exact SQL you are running, the odds of someone duplicating your issue and then fixing your issue go up 10-fold. I like fixing problems, not trying to replicate problems. <br>ATB,<br>P<br><br><blockquote type="cite">On Feb 24, 2025, at 7:38 AM, Frank Gevaerts <frank.gevaerts@fks.be> wrote:<br><br>Hello,<br><br>I'm having issues with ST_Reskew(). The source raster (32BSI) contains 150000 points, and ST_Reskew() takes forever. If I rescale the raster to anywhere under ~80000 points, it suddenly only takes around 300ms. This is not linear, ~85000 points is bad, and then suddenly 80000 points is good.<br><br>I'm not actually sure if it's "just" a performance problem or an infinite loop, I have not had the patience yet to have it run for more than 20 minutes.<br><br>This is using postgis 3.5.2 on debian installed from apt.postgresql.org, and libgdal36 3.10.2<br><br>Is there anything I'm overlooking, or is there a memory usage parameter I can set to help with this?<br><br>Frank<br></blockquote><br></blockquote><br>-- <br>Frank Gevaerts frank.gevaerts@fks.be<br>fks bvba - Formal and Knowledge Systems http://www.fks.be/<br>Grote Baan 79 Tel: ++32-(0)11-21 49 11<br>B-3511 KURINGEN-HASSELT Fax: ++32-(0)11-22 04 19<br></blockquote><br></div></div></blockquote></div><br></body></html>