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[FLINK-38810] Use splittable timers in Interval Join #27345

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[FLINK-38810] Use splittable timers in Interval Join #27345

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@rkhachatryan rkhachatryan commented Dec 15, 2025 •
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What is the purpose of the change

On timer, TimeIntervalJoin potentially performs a lot of work iterating through all it's records in state.

And when multiple timers are triggered by a single watermark, checkpoint can be delayed significantly, effectively increasing e2e latency.

Recently, splittable timers were introduced to Flink for a limited set of operators in FLINK-20217.

TimeIntervalJoin can benefit from it as well.

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flinkbot commented Dec 15, 2025 •
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CI report:

Bot commands The @flinkbot bot supports the following commands:
  • @flinkbot run azure re-run the last Azure build

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pnowojski commented Dec 17, 2025

I think change LGTM, but doesn't it lack test coverage? Are there some an existing tests for delayed watermarks?

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[hotfix] Set mailboxExecutor in AbstractStreamOperator constructor if…
d9b4652 
… available
@rkhachatryan
[FLINK-38810] Pull WM processing up from KeyedCoProcessOperatorWithWa…
770a21b 
…termarkDelay

This refactoring removes a separate code path for watermark processing
in KeyedCoProcessOperatorWithWatermarkDelay thus enabling the use of splittable timers.
@rkhachatryan
[FLINK-38810] Enable splittable timers in Interval Join
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@rkhachatryan rkhachatryan marked this pull request as ready for review January 8, 2026 23:23
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rkhachatryan commented Jan 8, 2026
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I've split the commit and added a test; although it focuses mostly on postponing timers (see comment below).

pnowojski
pnowojski approved these changes Jan 9, 2026
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rkhachatryan commented Jan 9, 2026

@flinkbot run azure

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rkhachatryan commented Jan 9, 2026

@flinkbot run azure

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