generate uuid/ id for table which do not have any primary key

[Vishal Swaroop]

How to generate uuid/ id (maybe in data-config.xml...) for table which do
not have any primary key.

Scenario :
Using DIH I need to import data from database but table does not have any
primary key
I do have uuid defined in schema.xml and is
<field name="uuid" type="uuid" indexed="true" stored="true" required="true"
multiValued="false"/>
<uniqueKey>uuid</uniqueKey>

data-config.xml
<?xml version="1.0" encoding="UTF-8" ?>
<dataConfig>
<dataSource
  batchSize="2000"
  name="test"
  type="JdbcDataSource"
  driver="oracle.jdbc.OracleDriver"
  url="jdbc:oracle:thin:@ldap:...."
  user="myUser"
  password="pwd"/>
<document>
<entity name="test_entity"
  docRoot="true"
  dataSource="test"
  query="select name, age from test_user">
</entity>
</document>
</dataConfig>

Error : Document is missing mandatory uniqueKey field: uuid