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Backport Fix featureCount on postgres view when flag estimatedmetadat…

…a is set
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troopa81 authored and nyalldawson committed Oct 4, 2019
1 parent 1f02010 commit 650005080b3d9b6dd5e4fe4da19efcad16ba3648
Showing with 33 additions and 5 deletions.
  1. +23 −5 src/providers/postgres/qgspostgresprovider.cpp
  2. +10 −0 tests/src/python/test_provider_postgres.py
@@ -3348,20 +3348,38 @@ 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( QStringLiteral( "Plan" ) ).toMap() : QVariantMap();
const QVariantList queryPlan = countPlan.value( QStringLiteral( "Plans" ) ).toList();
const QVariant nbRows = queryPlan.count() ? queryPlan[0].toMap().value( QStringLiteral( "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 ) );
@@ -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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