Github user kl0u commented on the issue:
https://github.com/apache/flink/pull/4550
From a brief check, I see that this also removed backwards compatibility
also for 1.2 for the CEP library. The reason is that the CEP library in Flink
1.2 was the same as in Flink 1.1 (no upgrade) and so it was using the old state
abstractions.
Given that in the ML we discussed about dropping compatibility with 1.1 and
agreed on that, a library should not affect that development, but there must be
an explicit discussion in the ML for this specific matter before merging it.
Even if this just means just saying that you have to go through 1.3 for CEP if
you want to migrate from 1.2 to 1.4.
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