GIVEN:
select a.name, b.sumary
from Opp a OUTER JOIN OLI b ON a.id = b.foreignId

JoinQueryVisitor of SFDC translator correctly creates:
select a.name, (select b.summary from OLI b) from Opp a

As of SFDC docs:
http://www.salesforce.com/us/developer/docs/api/index_Left.htm#StartTopic=Content/sforce_api_calls_soql_relationships.htm

you get a result set of for example:
"opp #1", [b] QueryResult for row #1
"opp #2", [b] QueryResult for row #2

Which must be transformed into something like this (EXPECTED)
"opp #1", 100
"opp #1", 150
"opp #1", 43000
"opp #2", 10000
"opp #2", 100
etc.

Right now, it gets transformed into something like (CURRENT)
"opp #1", null
"opp #2", null
"opp #3", null
etc.