diff --git a/lib/DatabaseStatistics.php b/lib/DatabaseStatistics.php
index 3a8b896f..10408406 100644
--- a/lib/DatabaseStatistics.php
+++ b/lib/DatabaseStatistics.php
@@ -97,30 +97,11 @@ protected function databaseSize(): string {
 				}
 				break;
 			case 'pgsql':
-				$sql = "SELECT proname
-					FROM pg_proc
-					WHERE proname = 'pg_database_size'";
-				$result = $this->connection->executeQuery($sql);
-				$row = $result->fetch();
+				$database = $this->config->getSystemValueString('dbname');
+				$sql = 'SELECT pg_database_size(:dbname) as size';
+				$result = $this->connection->executeQuery($sql, ['dbname' => $database]);
+				$database_size = $result->fetchOne();
 				$result->closeCursor();
-				if ($row['proname'] === 'pg_database_size') {
-					$database = $this->config->getSystemValue('dbname');
-					if (strpos($database, '.') !== false) {
-						[$database, ] = explode('.', $database);
-					}
-					$sql = "SELECT oid
-						FROM pg_database
-						WHERE datname = '$database'";
-					$result = $this->connection->executeQuery($sql);
-					$row = $result->fetch();
-					$result->closeCursor();
-					$oid = $row['oid'];
-					$sql = 'SELECT pg_database_size(' . $oid . ') as size';
-					$result = $this->connection->executeQuery($sql);
-					$row = $result->fetch();
-					$result->closeCursor();
-					$database_size = $row['size'];
-				}
 				break;
 			case 'oci':
 				$sql = 'SELECT SUM(bytes) as dbsize
diff --git a/lib/ShareStatistics.php b/lib/ShareStatistics.php
index 6ec599e6..423bba81 100644
--- a/lib/ShareStatistics.php
+++ b/lib/ShareStatistics.php
@@ -59,10 +59,14 @@ protected function countEntries(string $tableName): int {
 		$query->select($query->func()->count('*', 'num_entries'))
 			->from($tableName);
 		$result = $query->executeQuery();
-		$row = $result->fetch();
+		$row = $result->fetchOne();
 		$result->closeCursor();
 
-		return (int)$row['num_entries'];
+		if ($row === false) {
+			return 0;
+		}
+
+		return (int)$row;
 	}
 
 	/**
@@ -72,7 +76,7 @@ protected function countEntries(string $tableName): int {
 	 */
 	protected function countShares(int $type, bool $noPassword = false): int {
 		$query = $this->connection->getQueryBuilder();
-		$query->selectAlias($query->createFunction('COUNT(*)'), 'num_entries')
+		$query->select($query->func()->count('*', 'num_entries'))
 			->from('share')
 			->where($query->expr()->eq('share_type', $query->createNamedParameter($type)));
 
@@ -81,9 +85,13 @@ protected function countShares(int $type, bool $noPassword = false): int {
 		}
 
 		$result = $query->executeQuery();
-		$row = $result->fetch();
+		$row = $result->fetchOne();
 		$result->closeCursor();
 
-		return (int)$row['num_entries'];
+		if ($row === false) {
+			return 0;
+		}
+
+		return (int)$row;
 	}
 }
diff --git a/lib/StorageStatistics.php b/lib/StorageStatistics.php
index 0e14a759..5f17743d 100644
--- a/lib/StorageStatistics.php
+++ b/lib/StorageStatistics.php
@@ -95,9 +95,14 @@ protected function countStorages(string $type): int {
 			$query->andWhere($query->expr()->notLike('id', $query->createNamedParameter('local::%')));
 		}
 		$result = $query->executeQuery();
-		$row = $result->fetch();
+		$row = $result->fetchOne();
 		$result->closeCursor();
-		return (int)$row['num_entries'];
+
+		if ($row === false) {
+			return 0;
+		}
+
+		return (int)$row;
 	}
 
 	public function updateAppDataStorageStats(): void {