function checkEvalRelations_UniqueKeys(evalFn) {
  var sampleRows = getSampleRows();

  var employeeRelation = lf.proc.Relation.fromRows(
      sampleRows.employees, [e.getName()]);
  var jobRelation = lf.proc.Relation.fromRows(
      sampleRows.jobs, [j.getName()]);

  var joinPredicate1 = e.jobId.eq(j.id);
  var result = evalFn.call(
      joinPredicate1, employeeRelation, jobRelation, false);
  assertEquals(sampleRows.employees.length, result.entries.length);

  // Expecting only 5 result entries, since there are only 5 employees that have
  // the same ID with a job.
  var joinPredicate2 = e.id.eq(j.id);
  result = evalFn.call(
      joinPredicate2, employeeRelation, jobRelation, false);
  assertEquals(sampleRows.jobs.length, result.entries.length);
}
Checks that the given join implementation is correct, for the case where the
join predicate refers to unique keys.
@param {!function(!lf.proc.Relation, !lf.proc.Relation, boolean)
    :!lf.proc.Relation} evalFn The join implementation method should be
    either evalRelationsNestedLoopJoin_ or evalRelationsHashJoin_.