Parser interface docs; deprecate setFieldNames/getFieldNames.

[gianm]

• Docs for Parser
• Deprecated setFieldNames/getFieldNames. They don't appear to be used in meaningful ways anywhere in Druid, and I think are just confusing things by being on the interface.

[himanshug]

actually, thinking more about it, it seems support for fieldNames is useful for csv, tsv and the regex, javascript parsers in #36 unlike the JSONParser and they shouldn't be deprecated.

[gianm]

@himanshug the thought behind deprecating these was:

• external usages of setFieldNames are generally immediately after construction of a specific parser class. So those usages don't really need to use a setter- they could instead use a constructor that offers fieldNames (those constructors already exist but are not always used).
• these methods are actually pretty nonsensical for the JsonPath parser (Add JsonPath parser #34), because its FieldSpecs serve the same purpose, but they do it in a richer way that is specific to JsonPath.

So, I don't think these methods are really useful, nor do they generalize well to all parsers.

[himanshug]

ok, sounds reasonable, I agree field names do not make sense for json parsers but only for csv, tsv, regex parsers who can support those via specific constructors.

[himanshug]

👍

@xvrl @nishantmonu51 @drcrallen can one of you pls merge this?

[fjy]

👍