Kodo 2.5 Joins

Question

Manual says:
"Added the com.solarmetric.kodo.impl.jdbc.UseSQL92Joins configuration
property. Set this property to 'true' to use SQL 92-style joins in queries,
including left outer joins where appropriate. You can also set this property
on an individual query instance; see the
com.solarmetric.kodo.impl.jdbc.query.JDBCQuery class Javadoc for details."
Could you please clarify the "outer join issue". Do I have any control over
choosing inner or outer? I would not want to use outer if I can use inner
(non null oreign key enforced reference) - much faster

Answer 1

Patrick,
Any chance to make it work for collections too? Most of my staff is in
collections. I do not use queries very much. We want nice object model and
queries are really secondary. Unfortunately very often fetching this
collections is slow because (well fetching the collection itself is fine) of
lazy reference resolution on collection members.
In case joining is possible for collections we would need to be able to
enable/disable joining on PM level and also be able to configure in metadata
via fetch groups and explicit instructions which references I want joined.
"Patrick Linskey" <[email protected]> wrote in message
news:b5e9hr$ptu$[email protected]..
Alex Roytman wrote:
And also what controls joining?
- When is it used and when it is not? How to control itThe use of outer joins is determined by the nature of queries that you
execute. There aren't currently any user-available hints for outer join
control. In internal builds in which we know more information about
referential integrity constraints, we'll be able to do some more clever
decision-making.
- Can custom fetch groups and PM level fetch group definitions control
join
vs. lazy reference traversal?Custom fetch groups + fetch group config can be used to control whether or
not tables might be joined into initial queries, yes. But it does not
control the nature of whether we use outer or inner joins.
- Is it used on single objects? on queries? on collections reading?Queries.
Any plans to add fetch group config on query level too?Not currently, but probably someday. Currently, the closest you can get is
to change the PM, execute the query, and change back, which is less than
ideal if you're using the PM in multiple threads, but that's what you've
got for now.
-Patrick