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From GitBox <...@apache.org>
Subject [GitHub] [accumulo] hkeebler edited a comment on issue #1043: Support stable ~del split points and avoid ~del hotspots
Date Mon, 29 Jul 2019 13:18:54 GMT
hkeebler edited a comment on issue #1043: Support stable ~del split points and avoid ~del hotspots

URL: https://github.com/apache/accumulo/issues/1043#issuecomment-515987329
 
 
   Considering the migration strategy:
   
   > If this can be done, upgrade needs to be considered. Below are two possible upgrade
designs.
   > 
   >     Rewrite the metadata table on upgrade and recompute the split points.
   >     Support del entries with and without the hash. One possible way to do this is
with a different prefix like ~deh that indicates a hash is present.
   > 
   > May make sense to make the same change for the ~blip section of the metadata table
also.
   
   The first seems desirable because it does not require supporting two formats down the road.
 How costly is the metadata rewrite?  I'm thinking the metadata tables are much smaller than
data tables, the ~del<path> should be minimal especially if a GC is done first,  because
they are lumped together the cost of finding them is low.  Can you turn off compaction and
balancing (whatever) during a migration upgrade?  For ~blip, can you require that bulk imports
are all complete prior to the upgrade?

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