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Fix featureCount on postgres view when flag estimatedmetadata is set #32114

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merged 2 commits into from Nov 21, 2019
Merged

Fix featureCount on postgres view when flag estimatedmetadata is set #32114

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be4c4d3
Fix featureCount on postgres view when flag estimatedmetadata is set
troopa81 Oct 4, 2019
5f43b3f
Add pg version guard and test on estimated count for view
troopa81 Nov 7, 2019
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28 changes: 23 additions & 5 deletions src/providers/postgres/qgspostgresprovider.cpp
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Expand Up @@ -3332,20 +3332,38 @@ 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 = -1;
if ( !mIsQuery && mUseEstimatedMetadata )
{
sql = QStringLiteral( "SELECT reltuples::bigint FROM pg_catalog.pg_class WHERE oid=regclass(%1)::oid" ).arg( quotedValue( mQuery ) );
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
{
sql = QStringLiteral( "SELECT count(*) FROM %1%2" ).arg( mQuery, filterWhereClause() );
}
QgsPostgresResult result( connectionRO()->PQexec( sql ) );

QgsPostgresResult result( connectionRO()->PQexec( sql ) );
QgsDebugMsg( "number of features as text: " + result.PQgetvalue( 0, 0 ) );

QgsDebugMsg( "number of features as text: " + result.PQgetvalue( 0, 0 ) );
num = result.PQgetvalue( 0, 0 ).toLong();
}

long num = result.PQgetvalue( 0, 0 ).toLong();
mShared->setFeaturesCounted( num );

QgsDebugMsg( "number of features: " + QString::number( num ) );
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10 changes: 10 additions & 0 deletions tests/src/python/test_provider_postgres.py
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Expand Up @@ -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):

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