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<p class="MsoNormal"><span lang="FR" style="font-size:11.0pt;mso-fareast-language:EN-US">Thanks Regis.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="FR" style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US">I tried with an existing project, and with no project. The information of the layers is:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Lato",sans-serif;color:black">service='</span><span lang="EN-US" style="font-family:"Lato",sans-serif;color:black">mycomp_prod</span><span style="font-family:"Lato",sans-serif;color:black">' sslmode=require key='gid'
estimatedmetadata=true srid=27572 type=Point checkPrimaryKeyUnicity='1' table="public"."</span><span lang="EN-US" style="font-family:"Lato",sans-serif;color:black">mylayer</span><span style="font-family:"Lato",sans-serif;color:black">"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Lato",sans-serif;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Lato",sans-serif;color:black">with service in `.pg_service.conf` :<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Lato",sans-serif;color:black">[mycomp_prod]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Lato",sans-serif;color:black">user=rd<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Lato",sans-serif;color:black">sslmode=require<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Lato",sans-serif;color:black">host=gis.mycomp.fr<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Lato",sans-serif;color:black">port=5432<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Lato",sans-serif;color:black">dbname=mycomp<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Lato",sans-serif;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Lato",sans-serif;color:black">(don’t blame me for the 27572 OK
</span><span lang="EN-US" style="font-family:"Apple Color Emoji";color:black">😅</span><span lang="EN-US" style="font-family:"Lato",sans-serif;color:black">)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Lato",sans-serif;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Lato",sans-serif;color:black">I think I’ll open an issue because it _<i>seems</i>_ to do a SELECT count(*) FROM mylayer + SELECT * FROM mylayer until all features have been fetched. In my example,
I have a 11M Points layer so it takes a while </span><span lang="EN-US" style="font-family:"Apple Color Emoji";color:black">😊</span><span lang="EN-US" style="font-family:"Lato",sans-serif;color:black">.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">Régis Haubourg <regis.haubourg@gmail.com><br>
<b>Date: </b>Saturday, 25 June 2022 at 12:54<br>
<b>To: </b>Rémi Desgrange <remi.desgrange@ielo.net><br>
<b>Cc: </b>QGIS Developers List <qgis-developer@lists.osgeo.org><br>
<b>Subject: </b>Re: [QGIS-Developer] Feature count for DB provider.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Hi Rémy, There had been a lot of work for postGIS and oracle providers. A count(*) might be really expensive for big tables, so there are options to use db statistics instead of real count. I bet the loop
you point out occurs only in fallback situations but is not the main case.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">One is here for instance by there are numerous PRs like this one
<a href="https://github.com/qgis/QGIS/pull/37619">https://github.com/qgis/QGIS/pull/37619</a><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">In think @troopa81 has a clear view of the current state.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">all the best<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Régis <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Le sam. 25 juin 2022 à 10:38, Rémi Desgrange via QGIS-Developer <<a href="mailto:qgis-developer@lists.osgeo.org" target="_blank">qgis-developer@lists.osgeo.org</a>> a écrit :<o:p></o:p></span></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="FR" style="font-size:11.0pt">Hi,</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="FR" style="font-size:11.0pt"> </span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="font-size:11.0pt">Just launched the new QGIS 3.24, and tests the SQL debugger, I just found out that the “feature count” does a while loop on all features
in the layer to count.</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="font-size:11.0pt"> </span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="font-size:11.0pt">While it’s probably necessary for shapefiles or stuff like that, it appears suboptimal for databases access. I found this part in the
code that looks like to be responsible for the feature counts, <a href="https://github.com/qgis/QGIS/blob/master/src/core/vector/qgsvectorlayerfeaturecounter.cpp#L76-L90" target="_blank">
https://github.com/qgis/QGIS/blob/master/src/core/vector/qgsvectorlayerfeaturecounter.cpp#L76-L90</a>
</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="font-size:11.0pt"> </span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="font-size:11.0pt">Do you think I could make a special case for database-based provider (geopackage, postgres/oracle/mysql/etc…) that launch a “SELECT count(*)
FROM table” instead of looping on all features.</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="font-size:11.0pt"> </span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="font-size:11.0pt">Thanks.
</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
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