[GitHub] [lucene-solr] mikemccand commented on pull request #1543: LUCENE-9378: Disable compression on binary values whose length is less than 32.

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mikemccand commented on pull request #1543:
URL: https://github.com/apache/lucene-solr/pull/1543#issuecomment-669227131


   Thinking more above the above proposal, specifically this line, which is OK for our usage but I think not so great for other users who would like to reduce or turn off the `BINARY` doc values compression:
   
   > This would mean that your indices would no longer have backward compatibility guarantees of the default codec (N-1) but maybe you don't care since you're re-building your indices from scratch on a regular basis?
   
   We lose backwards compatibility because we would have to create our own named `Codec`, using our own custom `DocValuesFormat`?
   
   But, couldn't we instead just subclass Lucene's default codec, override {{getDocValuesFormatPerField}} to subclass {{Lucene80DocValuesFormat}} (oh, I see, yeah we cannot do that -- this class is `final`, which makes sense).  I was thinking since this (whether to compress each block) is purely a write time decision, it could still be done as `Lucene80` doc values format SPI.
   
   So yeah we would lose backwards compatibility, but it's a trivially small piece of code to carry that custom `Codec` forward, so it is not that big a deal.
   
   But then I wonder why not just add a `boolean compress` option to `Lucene80DocValuesFormat`?  This is similar to the compression `Mode` we pass to stored fields and term vectors format at write time, and it'd allow users who would like to disable `BINARY` doc values compression to keep backwards compatibility.


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