CASSANDRA-21154 remove traces of sampling and auto training

[smiklosovic]

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The Cassandra Jira

[smiklosovic]

to shut up idea code style

[smiklosovic]

I am not completely sure about this staying here. We are technically not sampling anymore. SAMPLING is the state after we do "start" and we depend on this state when we go to train. It would be probably better to replace it with "started".

[smiklosovic]

It would be also maybe better if we called "start" method of ICompressionDictionaryTrainer like "init" instead of "start". We have not started anything and we are not sampling either. The javadoc of start method says

Starts the trainer for collecting samples.

We are not doing that anymore.

[yifan-c]

I think the "SAMPLING" status still make sense. The current and only approach to collect training data is to perform random sampling on the the on-disk sstables.

[smiklosovic]

also

logger.info("Started dictionary training for {}.{}", keyspaceName, tableName);

below is suspicious. I would not log anything, actually.

[yifan-c]

Agreed on the log message removal. Given that, the training is manual, the log message to indicate the start of the process is less useful.

[yifan-c]

Looks good overall. Thank you for tidying up the currently unused code in the dictionary compression domain!