alamb commented on PR #7821:
URL: 
https://github.com/apache/arrow-datafusion/pull/7821#issuecomment-1779708060

   > 
   My understanding is that bloom filter returns false positives which you have 
to filter exactly (without a bloom filter) in a second step. I was referring to 
the second step. I never wrote such algorithm before so there is a good chance 
I don’t know what I’m talking about 😅
   
   
   
   Hi @alippai  -- what this PR does is use the (optional) Bloom Filter that is 
stored in parquet files to evaluate equality predicates more efficiently -- for 
example, `a = 4` type predicates.
   
   In general it would be interesting to contemplate using a bloom filter for 
COUNT(distinct ...) type predicates, though the existing hash table based 
implementation is pretty fast 


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