I agree with Jark. It reduces confusion.
The DataStream API doesn't know changelog processing at all. A
DataStream of Row can be used with both `fromDataStream` and
`fromChangelogStream`. But only the latter API will interpret it as a
changelog something.
And as I mentioned before, the `toChangelogStream` must work with Row
otherwise users are confused due to duplicate records with a missing
changeflag.
I will update the FLIP-136 a last time. I hope we can then continue to a
vote.
Regards,
Timo
On 09.09.20 10:50, Danny Chan wrote:
I think it would bring in much confusion by a different API name just because
the DataStream generic type is different.
If there are ChangelogMode that only works for Row, can we have a type check
there ?
Switch to a new API name does not really solve the problem well, people still
need to declare the ChangelogMode explicitly, and there are some confusions:
• Should DataStream of Row type always use #fromChangelogStream ?
• Does fromChangelogStream works for only INSERT ChangelogMode ?
Best,
Danny Chan
在 2020年9月9日 +0800 PM4:21，Timo Walther <twal...@apache.org>，写道：
I had this in the inital design, but Jark had concerns at least for the
`toChangelogStream(ChangelogMode)` (see earlier discussion).
`fromDataStream(dataStream, schema, changelogMode)` would be possible.
But in this case I would vote for a symmetric API. If we keep
toChangelogStream we should also have a fromChangelogStream.
And if we unify `toChangelogStream` and `toDataStream`, retractions
cannot be represented for non-Rows and users will experience duplicate
records with a missing changeflag.
Regards,
Timo
On 09.09.20 09:31, Danny Chan wrote:
“But I think the planner needs to
know whether the input is insert-only or not.”
Does fromDataStream(dataStream, schema, changelogMode)
solve your concerns ? People can pass around whatever ChangelogMode they like
as an optional param.
By default: fromDataStream(dataStream, schema), the ChangelogMode is INSERT.
Best,
Danny Chan
在 2020年9月9日 +0800 PM2:53，dev@flink.apache.org，写道：
But I think the planner needs to
know whether the input is insert-only or not.
