keith-turner opened a new issue #1383: Make scan execution hints influence 
caching.
URL: https://github.com/apache/accumulo/issues/1383
 
 
   There are two use cases I was recently thinking through were I thought it 
would be nice to not cache data.  One was when the Accumulo garbage collector 
scans the metadata table for deletion and blip markers.  Another is when Fluo 
scan for notifications.  In both cases the data is only scanned sequentially 
and never accessed randomly. 
   
   There are a few possible ways this could accomplished using execution hints. 
 
   
     1. The execution hints could be passed to the cache directly 
     2. Scan dispatchers could disable cache for a scan based on execution 
hints.
     3. A new per table plugin could be created that makes caching decisions 
based on execution hints.
   
   Options 1 would probably lead to the cache (which is currently a tablet 
server level entitiy) needing per table config.  Options 2 and 3 do not have 
this problem.
   
   For notifications scans, Fluo is already [setting a 
hint](https://fluo.apache.org/blog/2019/09/30/scan-executors/) of 
`scan_type=fluo-ntfy`.  So if cache could be configured to be diabled this 
scan_type, thne Fluo could benefit.

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