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Posted to user@flink.apache.org by yunfan123 <yu...@foxmail.com> on 2017/08/17 04:07:37 UTC
Why ListState of flink don't support update?
If I want to update the list.
I have to do two steps:
listState.clear()
for (Element e : myList) {
listState.add(e);
}
Why not I update the state by:
listState.update(myList) ?
--
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Re: Why ListState of flink don't support update?
Posted by Stefan Richter <s....@data-artisans.com>.
Having a second look, I think what you are suggesting is just a change to the API, so that should work but it is not there. You could open a Jira to suggest this.
> Am 17.08.2017 um 06:07 schrieb yunfan123 <yu...@foxmail.com>:
>
> If I want to update the list.
> I have to do two steps:
> listState.clear()
> for (Element e : myList) {
> listState.add(e);
> }
>
> Why not I update the state by:
> listState.update(myList) ?
>
>
>
> --
> View this message in context: http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Why-ListState-of-flink-don-t-support-update-tp14957.html
> Sent from the Apache Flink User Mailing List archive. mailing list archive at Nabble.com.
Re: Why ListState of flink don't support update?
Posted by Stefan Richter <s....@data-artisans.com>.
Hi,
this is because the list state is intended to be append only. The underlying reason is that this allows certain optimizations in the underlying datastructures. For example, a list state for the RocksDB backend can make use of RocksDB’s merge operator and does not require a full rewrite to the DB on appends.
If you need to have a list that supports this, you could use a value state of type list or use a map state where you map from list-index -> element.
Best,
Stefan
> Am 17.08.2017 um 06:07 schrieb yunfan123 <yu...@foxmail.com>:
>
> If I want to update the list.
> I have to do two steps:
> listState.clear()
> for (Element e : myList) {
> listState.add(e);
> }
>
> Why not I update the state by:
> listState.update(myList) ?
>
>
>
> --
> View this message in context: http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Why-ListState-of-flink-don-t-support-update-tp14957.html
> Sent from the Apache Flink User Mailing List archive. mailing list archive at Nabble.com.