[FLINK-15741][docs][TTL] Fix TTL docs after enabling RocksDB compaction filter by default

[azagrebin]

What is the purpose of the change

RocksDB compaction filter is always enabled by default after #10866 and we deprecated its disabling. The docs should not refer to its enabling/disabling. The Chinese translation still has to be adjusted separately.

Brief change log

adjust state.md

Verifying this change

doc change

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (no)
• The serializers: (no)
• The runtime per-record code paths (performance sensitive): (no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: (no)
• The S3 file system connector: (no)

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (docs)

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Automated Checks

Last check on commit 7ac3802 (Thu Jan 23 14:50:39 UTC 2020)

Warnings:

• Documentation files were touched, but no .zh.md files: Update Chinese documentation or file Jira ticket.

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[GJL]

It's ok. It's up to you whether you want to address my suggestions.

[GJL]

Imo, "when" is not needed.

Maybe another alternative that sounds better to me: [...] queries the current timestamp for every 1000 processed entries

[GJL]

Currently it sounds like that the cleanup strategy won't be active by default or there are other strategies that can be used – Maybe that's just me. My proposal would be:

If the RocksDB state backend is used, a Flink specific compaction filter will be employed to enable background cleanup.

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CI report:

• 04f0541 Travis: SUCCESS Azure: FAILURE

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[azagrebin]

Thanks for the review @GJL
I addressed the comments, merging this

[azagrebin]

merge into master by 05bddfb
merge into 1.10 by 52a7ac9