This is mostly a remnant from the previous state API, see [1] for
reference. The behaviour was basically copied to the new state
implementations, which was a mistake, in hindsight. Also see [2] where I
added AppendingState, here I also didn't document any special null
behaviour.
Best,
Aljoscha
[1]
https://github.com/apache/flink/commit/caf46728045c0b886e6d4ec0aa429a830740a391
[2]
https://github.com/apache/flink/commit/6cd8ceb10c841827cf89b74ecf5a0495a6933d53
On 16.01.20 04:13, Yun Tang wrote:
+1 for unifying the behavior of AppendingState#add .
However, I have concern for the usage of window reducing function [1], I'm not
sure whether user would rely on processing StreamRecord(null) to clear state.
As you can see, user could not see the reducing window state directly, and the
only way to communicate with state is via processing records.
I'm not sure whether this is by design, @Aljoscha
Krettek<mailto:aljos...@apache.org> would you please share the initial idea
when introducing this for the first time?
[1]
https://ci.apache.org/projects/flink/flink-docs-stable/dev/stream/operators/windows.html#reducefunction
Best
Yun Tang
________________________________
From: Yu Li <car...@gmail.com>
Sent: Thursday, January 9, 2020 14:09
To: dev <dev@flink.apache.org>
Subject: Re: [DISCUSS] Make AppendingState#add refuse to add null element
+1 for unifying the behavior to refusing adding null element. Nice catch
and thanks for bringing up the discussion!
Best Regards,
Yu
On Wed, 8 Jan 2020 at 22:50, Aljoscha Krettek <aljos...@apache.org> wrote:
Hi,
As I said in the discussion on the Jira issue, I’m in favour of this
change!
This is the Jira Issue, for reference:
https://issues.apache.org/jira/browse/FLINK-15424
Best,
Aljoscha
On 8. Jan 2020, at 15:16, Congxian Qiu <qcx978132...@gmail.com> wrote:
Dear All
Currently, we found the implementations of AppendingState#add are not the
same, taking some as example:
- HeapReducingState will clear state if add null element
- RocksDBReducingState will add null element if serializer can
serialize
null
- Both HeapListState and RocksDBListState refuse to add null element —
will throw NullPointException
we think this need to be fixed, and possible solutions include:
1. Respect the current java doc, which said “If null is passed in, the
state value will remain unchanged”
2. Make all AppendingState#add refuse to add null element
We propose to apply the second solution, following the recommendation in
Guava[1].
Would love to hear your thoughts. Thanks.
Regards,
Congxian
[1] https://github.com/google/guava/wiki/UsingAndAvoidingNullExplained
