jordepic commented on issue #1026:
URL: https://github.com/apache/iceberg/issues/1026#issuecomment-4239880046

   After speaking with @rdblue at the iceberg summit I may try and take this 
one on but with a spark procedure for going from equality deletes to deletion 
vectors.  Will use spark SQL for the expensive part (actually doing the row 
joining) in order to let spark do the majority of the join planning.
   
   After thinking about this problem a bit more, it does begin to beg the 
question how much streaming writes might actually benefit from secondary 
indices.  We currently flush many equality deletes at a time (in flink for 
example, one per incoming data row). Performing an asynchronous deletion 
conversion in spark while using an index really only benefits if we perform a 
nested loop join, which could get quite expensive with big equality delete 
files (as opposed to doing a hash join that doesn't require an index). 
   
   It really all depends on the relative size of the incoming deletes to 
convert versus the data partition size.  Happy to hear any other thoughts here. 
 I'll follow up if I push a commit.


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