Add pg version guard and test on estimated count for view

qgis · Nov 7, 2019 · 5f43b3f · 5f43b3f
1 parent be4c4d3
commit 5f43b3f
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Showing 2 changed files with 29 additions and 16 deletions.
diff --git a/src/providers/postgres/qgspostgresprovider.cpp b/src/providers/postgres/qgspostgresprovider.cpp
@@ -3332,24 +3332,27 @@ long QgsPostgresProvider::featureCount() const
   // use estimated metadata even when there is a where clause,
   // although we get an incorrect feature count for the subset
   // - but make huge dataset usable.
-  long num = 0;
+  long num = -1;
   if ( !mIsQuery && mUseEstimatedMetadata )
   {
-    // parse explain output to estimate feature count
-    // we don't use pg_class reltuples because it returns 0 for view
-    sql = QStringLiteral( "EXPLAIN (FORMAT JSON) SELECT count(*) FROM %1%2" ).arg( mQuery, filterWhereClause() );
-    QgsPostgresResult result( connectionRO()->PQexec( sql ) );
-
-    const QString json = result.PQgetvalue( 0, 0 );
-    const QVariantList explain = QgsJsonUtils::parseJson( json ).toList();
-    const QVariantMap countPlan = explain.count() ? explain[0].toMap().value( "Plan" ).toMap() : QVariantMap();
-    const QVariantList queryPlan = countPlan.value( "Plans" ).toList();
-    const QVariant nbRows = queryPlan.count() ? queryPlan[0].toMap().value( "Plan Rows" ) : QVariant();
-
-    if ( nbRows.isValid() )
-      num = nbRows.toInt();
-    else
-      QgsLogger::warning( QStringLiteral( "Cannot parse JSON explain result to estimate feature count (%1) : %2" ).arg( sql, json ) );
+    if ( connectionRO()->pgVersion() >= 90000 )
+    {
+      // parse explain output to estimate feature count
+      // we don't use pg_class reltuples because it returns 0 for view
+      sql = QStringLiteral( "EXPLAIN (FORMAT JSON) SELECT count(*) FROM %1%2" ).arg( mQuery, filterWhereClause() );
+      QgsPostgresResult result( connectionRO()->PQexec( sql ) );
+
+      const QString json = result.PQgetvalue( 0, 0 );
+      const QVariantList explain = QgsJsonUtils::parseJson( json ).toList();
+      const QVariantMap countPlan = explain.count() ? explain[0].toMap().value( "Plan" ).toMap() : QVariantMap();
+      const QVariantList queryPlan = countPlan.value( "Plans" ).toList();
+      const QVariant nbRows = queryPlan.count() ? queryPlan[0].toMap().value( "Plan Rows" ) : QVariant();
+
+      if ( nbRows.isValid() )
+        num = nbRows.toInt();
+      else
+        QgsLogger::warning( QStringLiteral( "Cannot parse JSON explain result to estimate feature count (%1) : %2" ).arg( sql, json ) );
+    }
   }
   else
   {

diff --git a/tests/src/python/test_provider_postgres.py b/tests/src/python/test_provider_postgres.py
@@ -1415,6 +1415,16 @@ def testCheckTidPkOnViews(self):
         for f in vl0.getFeatures():
             self.assertNotEqual(f.attribute(0), NULL)
 
+    def testFeatureCountEstimatedOnView(self):
+        """
+        Test feature count on view when estimated data is enabled
+        """
+        self.execSQLCommand('DROP VIEW IF EXISTS qgis_test.somedataview')
+        self.execSQLCommand('CREATE VIEW qgis_test.somedataview AS SELECT * FROM qgis_test."someData"')
+        vl = QgsVectorLayer(self.dbconn + ' 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)
+
 
 class TestPyQgsPostgresProviderCompoundKey(unittest.TestCase, ProviderTestCase):