presto-accumulo/src/main/java/io/prestosql/plugin/accumulo/io/AccumuloPageSink.java/AccumuloPageSink/toMutation
class AccumuloPageSink:    public static Mutation toMutation(Row row, int rowIdOrdinal, List<AccumuloColumnHandle> columns, AccumuloRowSerializer serializer)
    {
        // Set our value to the row ID
        Text value = new Text();
        Field rowField = row.getField(rowIdOrdinal);
        if (rowField.isNull()) {
            throw new PrestoException(INVALID_FUNCTION_ARGUMENT, "Column mapped as the Accumulo row ID cannot be null");
        }

        setText(rowField, value, serializer);

        // Iterate through all the column handles, setting the Mutation's columns
        Mutation mutation = new Mutation(value);

        // Store row ID in a special column
        mutation.put(ROW_ID_COLUMN, ROW_ID_COLUMN, new Value(value.copyBytes()));
        for (AccumuloColumnHandle columnHandle : columns) {
            // Skip the row ID ordinal
            if (columnHandle.getOrdinal() == rowIdOrdinal) {
                continue;
            }

            // If the value of the field is not null
            if (!row.getField(columnHandle.getOrdinal()).isNull()) {
                // Serialize the value to the text
                setText(row.getField(columnHandle.getOrdinal()), value, serializer);

                // And add the bytes to the Mutation
                mutation.put(columnHandle.getFamily().get(), columnHandle.getQualifier().get(), new Value(value.copyBytes()));
            }
        }

        return mutation;
    }