presto-main/src/main/java/io/prestosql/sql/planner/NodePartitioningManager.java/NodePartitioningManager/getConnectorBucketNodeMap
class NodePartitioningManager:    private ConnectorBucketNodeMap getConnectorBucketNodeMap(Session session, PartitioningHandle partitioningHandle)
    {
        checkArgument(!(partitioningHandle.getConnectorHandle() instanceof SystemPartitioningHandle));

        ConnectorNodePartitioningProvider partitioningProvider = partitioningProviders.get(partitioningHandle.getConnectorId().get());
        checkArgument(partitioningProvider != null, "No partitioning provider for connector %s", partitioningHandle.getConnectorId().get());

        ConnectorBucketNodeMap connectorBucketNodeMap = partitioningProvider.getBucketNodeMap(
                partitioningHandle.getTransactionHandle().orElse(null),
                session.toConnectorSession(),
                partitioningHandle.getConnectorHandle());

        checkArgument(connectorBucketNodeMap != null, "No partition map %s", partitioningHandle);
        return connectorBucketNodeMap;
    }