On Tuesday, July 9, 2019 at 1:14:52 PM UTC-7, marc halperin wrote:
>
> I need to be able to take a Dataset object and for any join's where both
> tables contain a particular column 'x' I want to add to the on condition
> '... AND A.x=B.x' (where A and B are the tables already set to be join in
> the Dataset object). It looks like I may be able to manipulate the
> JoinOnClause objects associated with the Dataset object by getting
> opts[:join] but I wasn't sure if there were any specialized functions for
> doing this like select_append is for selects.
>
Unfortunately, there can be more than two tables in a dataset. For only
two tables, you could do something like:
DB.extend_datasets do
def join_table(_, table, *)
return super if opts[:join]
ds = super
join = ds.opts[:join][0]
if join.is_a?(Sequel::SQL::JoinOnClause)
if db.from(join.table_expr).columns.include?(:x) &&
columns.include?(:x) && join.on.is_a?(Sequel::SQL::BooleanExpression)
ds = ds.clone(:join=>[Sequel::SQL::JoinOnClause.new(join.on &
{Sequel.qualify(join.table, :x) => Sequel.qualify(first_source, :x)},
join.join_type, join.table_expr)])
end
end
ds
end
end
Thanks,
Jeremy
--
You received this message because you are subscribed to the Google Groups
"sequel-talk" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/sequel-talk.
To view this discussion on the web visit
https://groups.google.com/d/msgid/sequel-talk/caa2940e-49a9-4ba6-9458-0fb6333785d7%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
