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https://issues.apache.org/jira/browse/THRIFT-409?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12689632#action_12689632
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Bryan Duxbury commented on THRIFT-409:
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bq. Just use the struct format.
I thought of this as an option, but I think that will lead to suboptimal wire
performance. For instance, we definitely do not need a whole extra stop byte at
the end of the union just to say there's nothing more coming. There should only
ever be one field, so I say let's tailor it accordingly.
bq. That doesn't really work in containers, and I think it actually makes the
code quite a bit trickier in structs. Maybe we could have a special setting for
each union indicating that none of the fields are set.
I'll admit I'm not sure on how the container thing might work, but I don't
think it will make the struct code that much more complicated. I was thinking
that our generated union classes would have a static read() method that could
return null if an invalid union was read from the wire. If a null union is
unacceptable in any circumstance, I think we should just use some constant
"invalid" union or something to indicate there was a problem. However, I don't
think an empty union should be serializable.
bq. Do you mean "which of its fields is set"
Yep.
bq. Also, there is no need to add any new syntax for this while we are
experimenting with it. We can just make it an annotation.
Maybe. I think we'd kind of have to do a lot of working around the built in
generator behavior to do this, and if we ultimately decide to have this
feature, it'd be silly to use annotations for it.
> Add "union" to Thrift
> ---------------------
>
> Key: THRIFT-409
> URL: https://issues.apache.org/jira/browse/THRIFT-409
> Project: Thrift
> Issue Type: New Feature
> Reporter: Bryan Duxbury
> Fix For: 0.2
>
>
> It would be very helpful to have a "union" construct in Thrift. Let's decide
> on the design and then break up into sub-issues to add this feature.
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