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https://issues.apache.org/jira/browse/FLINK-13503?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16896865#comment-16896865
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Jingsong Lee commented on FLINK-13503:
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> however I think when T.id is null, we should not send request to
> DimensionTable to lookup datas, it's responsibility of LookupJoin operator to
> handle the case instead of Dimension connector.
Yeah, this is not behavior of temporal join, this is the bug in our internal
implementation.
Just like regular join, StreamExecLookupJoin/BatchExecLookupJoin should deal
with filterNulls and decide whether filter nulls outside connectors.
> Add contract in `LookupableTableSource` to specify the behavior when
> lookupKeys contains null
> ---------------------------------------------------------------------------------------------
>
> Key: FLINK-13503
> URL: https://issues.apache.org/jira/browse/FLINK-13503
> Project: Flink
> Issue Type: Task
> Components: Connectors / JDBC, Table SQL / API
> Affects Versions: 1.9.0, 1.10
> Reporter: Jing Zhang
> Assignee: Jing Zhang
> Priority: Minor
>
> I think we should add contract in `LookupableTableSource` to specify expected
> behavior when the lookupKeys contains null value.
> For example, one input record of eval method is (null,1) which means to look
> up data in (a,b) columns which key satisfy the requirement. there are at
> least three possibility here.
> * to ignore null value, that is, in the above example, only looks `b = 1`
> * to lookup `is value`, that is, in the above example, only looks `a is
> null and b = 1`
> * to return empty records, that is, in the above example, only looks `a =
> null and b = 1`
> In fact, there are different behavior in current code.
> For example, in Jdbc connector,
> The query template in `JdbcLookUpFunction` like:
> SELECT c, d, e, f from T where a = ? and b = ?
> If pass (null, 1) to `eval` method, it will generate the following query:
> SELECT c, d, e, f from T where a = null and b = 1
> Which always outputs empty records.
> BTW, Is this behavior reasonable?
> and the `InMemoryLookupableTableSource` behaviors like point 2 in the above
> list.
> some private connector in Blink behaviors like point 1
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