Rich-T-kid commented on PR #23187:
URL: https://github.com/apache/datafusion/pull/23187#issuecomment-5193036812

   So I think some nice follow ups would be
   
   1. expose a parquet dictionary encoding read flag to users
   2. allow a way to read only specific string columns as dictionary encoded 
(this may already be possible I need to check)
   
   by hand we can experiment with transforming low-card string group keys into 
`Dict<k,v>` and then #22891 will be in a position to be implemented. it may be 
possible to use column statistics as a guide for "low cardinality" columns but 
due to the state of statistics in datafusion this may or may not be accurate. 
ideally this will be tunable as either a hard set value or a percentage. There 
are some other issues that come to mind like schema management but I think its 
best to leave that in #22891's thread


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