Add comments to the Func definition

[MichelHollands]

Explain the filter func better. This was mentioned as a review comment in #5879.

Checklist

• Documentation added
• Tests updated
• Is this an important fix or new feature? Add an entry in the CHANGELOG.md.
• Changes that require user attention or interaction to upgrade are documented in docs/sources/upgrading/_index.md

Signed-off-by: Michel Hollands michel.hollands@grafana.com

[sandeepsukhani]

Would it be possible to move Func to either of deletion or chunkenc package i.e where it is used?

[chaudum]

I find it very problematic to name a function type just Func. Wouldn't it be better to name it after its functionality?

[DylanGuedes]

WDYT of naming it Predicate? I think it is how Apache Spark and Java name a similar thing.

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