It's now looking like QueryAssemblerHelper can also record whether
something is an outer join when creating the join list at the same
time it's outputting the column names.
Yes - qualifiers are translated as a separate piece.
One thing that is going to be annoying is having to specify an outer
join for every expression. I'm thinking we could have an "effective
outer join" value which, if not specified on the current Expression,
inherits from the parent expression. So an Expression join type by
default would be "unspecified" which means ask the parent. Any root
expression with unspecified would default to an inner join.
That's where I disagree - when you build a query, every outer join is
unique and unrelated to anything else. What I was thinking we can do
to simplify the semantics specification (and also make expressions
parsed from strings work the same way as expressions created via
ExpressionFactory) is add join type to the object path string. E.g.
use a "+" sign like Oracle did in the past:
* Inner join: "toArtist"
* Left outer join: "toArtist+"
* Longer path with mixed joins: "toGallery+.toAddress"
This seems like a reasonable non-verbose solution. What do you think?
Andrus
On Aug 17, 2006, at 3:34 PM, Mike Kienenberger wrote:
On 8/17/06, Mike Kienenberger <[EMAIL PROTECTED]> wrote:
On 8/17/06, Andrus Adamchik <[EMAIL PROTECTED]> wrote:
> > simply have a query.setJoinType(JoinType.OUTER) to enable and
disable
>
> I would say this should be done in Expression, not Query, as this
> affects individual joins.
Technically, I think it's going to be challenging to implement
this at
the Expression level rather than the query level. By the time the
SelectTranslator gets involved, it looks to me like the joins have
all
already been disassociated with the Expressions. It's unclear to me
whether all of the qualifiers have been disassociated with the
expressions at this point, but I think this wouldn't be a problem.
At least in Oracle, I need to add a (+) after every outer-joined-
table
column name in the join qualifiers ["db relationship joins"] and
after
every outer-joined-table column name in the selection qualifiers
["parent qualifier"].
I think in my own use cases, like Øyvind's, I'm ok with everything
being an outer join if anything is an outer join.
Oops. I wasn't quite ready to hit send yet -- I was still working
through all of this :-)
It's now looking like QueryAssemblerHelper can also record whether
something is an outer join when creating the join list at the same
time it's outputting the column names.
So, perhaps I spoke too soon.
One thing that is going to be annoying is having to specify an outer
join for every expression. I'm thinking we could have an "effective
outer join" value which, if not specified on the current Expression,
inherits from the parent expression. So an Expression join type by
default would be "unspecified" which means ask the parent. Any root
expression with unspecified would default to an inner join.
