Hi all, searching for the source of a QGIS issue https://github.com/qgis/QGIS/issues/35016, after testing various QGIS and GDAL version on Windows and Ubuntu Linux, I found that OGR fails to open a VRT layer file, with a remote data source (a csv file) hosted on data.world server, if VSI_CACHE is set to TRUE.
The QGIS issue was spotted on Windows since the OSGeo4W QGIS installer sets by default VSI_CACHE=TRUE and VSI_CACHE_SIZE=1000000: it seems these settings were introduced 7 years ago [1] to workaround a reported OGR performance issue [2] about shapefile reading over network on Windows. A test VRT file is available at https://raw.githubusercontent.com/agiudiceandrea/TEST_CSV/master/covid19-regioni_dw.vrt On both Windows (7 / 10 with GDAL/OGR 3.0.4 - 3.2.0dev) and Ubuntu Linux (20.04 / 18.04 with GDAL/OGR 3.0.4 - 2.2.3) if VSI_CACHE is not set or set to FALSE ogrinfo covid19-regioni_dw.vrt jgsghstpphjhicstradhy5kpjwrnfy -summary outputs INFO: Open of `covid19-regioni_dw.vrt' using driver `OGR_VRT' successful. Warning 6: Unknown type : data ... Layer name: jgsghstpphjhicstradhy5kpjwrnfy Geometry: Point Feature Count: 30069 Extent: (0.000000, 0.000000) - (18.171897, 46.499335) Layer SRS WKT: GEOGCRS["WGS 84", DATUM["World Geodetic System 1984", ELLIPSOID["WGS 84",6378137,298.257223563, LENGTHUNIT["metre",1]]], PRIMEM["Greenwich",0, ANGLEUNIT["degree",0.0174532925199433]], CS[ellipsoidal,2], AXIS["geodetic latitude (Lat)",north, ORDER[1], ANGLEUNIT["degree",0.0174532925199433]], AXIS["geodetic longitude (Lon)",east, ORDER[2], ANGLEUNIT["degree",0.0174532925199433]], ID["EPSG",4326]] Data axis to CRS axis mapping: 2,1 denominazione_regione: String (0.0) and QGIS can properly display the layer while if VSI_CACHE is set to TRUE ogrinfo covid19-regioni_dw.vrt jgsghstpphjhicstradhy5kpjwrnfy -summary outputs INFO: Open of `covid19-regioni_dw.vrt' using driver `OGR_VRT' successful. ERROR 1: Failed to open datasource `CSV:/vsicurl_streaming/https://query.data.world/s/jgsghstpphjhicstradhy5kpjwrnfy'. Layer name: jgsghstpphjhicstradhy5kpjwrnfy Geometry: None Feature Count: 0 Layer SRS WKT: (unknown) and QGIS cannot display the layer. Could the issue be caused by a server misconfiguration or not suitable for this kind of use, or should it be fixed in GDAL/OGR? Do you think the VSI_CACHE=TRUE 7 years old workaround setting is really still required on Windows (OSGeo4W), since in the meantime GDAL/OGR may have been improved in shapefile reading over network? If it could help, I can provide further analysis on HTTPS traffic and QGIS debug log during the connection attempts. Best regards. Andrea Giudiceandrea [1] https://github.com/qgis/QGIS/commit/9222f152b30948a3a9d9f66dffd162548022f7fd [2] https://lists.osgeo.org/pipermail/gdal-dev/2013-April/036077.html https://issues.qgis.org/issues/6448 | https://github.com/qgis/QGIS/issues/15688 -- Sent from: http://osgeo-org.1560.x6.nabble.com/GDAL-Dev-f3742093.html _______________________________________________ gdal-dev mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/gdal-dev
