[postgres] Fixes #40162 : Don't use explain plan when estimating coun…

…t on table

(cherry picked from commit 6c1a9bc)

src/providers/postgres/qgspostgresprovider.cpp

@@ -3588,7 +3588,7 @@ long QgsPostgresProvider::featureCount() const
   long num = -1;
   if ( !mIsQuery && mUseEstimatedMetadata )
   {
-    if ( connectionRO()->pgVersion() >= 90000 )
+    if ( relkind() == Relkind::View && connectionRO()->pgVersion() >= 90000 )
     {
       // parse explain output to estimate feature count
       // we don't use pg_class reltuples because it returns 0 for view
@@ -3605,6 +3605,12 @@ long QgsPostgresProvider::featureCount() const
       else
         QgsLogger::warning( QStringLiteral( "Cannot parse JSON explain result to estimate feature count (%1) : %2" ).arg( sql, json ) );
     }
+    else
+    {
+      sql = QStringLiteral( "SELECT reltuples::bigint FROM pg_catalog.pg_class WHERE oid=regclass(%1)::oid" ).arg( quotedValue( mQuery ) );
+      QgsPostgresResult result( connectionRO()->PQexec( sql ) );
+      num = result.PQgetvalue( 0, 0 ).toLong();
+    }
   }
   else
   {

tests/src/python/test_provider_postgres.py

@@ -2296,6 +2296,17 @@ def testCheckTidPkOnViews(self):
         for f in vl0.getFeatures():
             self.assertNotEqual(f.attribute(0), NULL)
 
+    def testFeatureCountEstimatedOnTable(self):
+        """
+        Test feature count on table when estimated data is enabled
+        """
+        vl = QgsVectorLayer(
+            self.dbconn +
+            ' sslmode=disable key=\'pk\' estimatedmetadata=true srid=4326 type=POINT table="qgis_test"."someData" (geom) sql=',
+            'test', 'postgres')
+        self.assertTrue(vl.isValid())
+        self.assertTrue(vl.featureCount() > 0)
+
     def testFeatureCountEstimatedOnView(self):
         """
         Test feature count on view when estimated data is enabled
@@ -2308,7 +2319,7 @@ def testFeatureCountEstimatedOnView(self):
             ' sslmode=disable key=\'pk\' estimatedmetadata=true srid=4326 type=POINT table="qgis_test"."somedataview" (geom) sql=',
             'test', 'postgres')
         self.assertTrue(vl.isValid())
-        self.assertTrue(self.source.featureCount() > 0)
+        self.assertTrue(vl.featureCount() > 0)
 
     def testIdentityPk(self):
         """Test a table with identity pk, see GH #29560"""