justinborromeo commented on a change in pull request #7133: Time Ordering On 
Scans
URL: https://github.com/apache/incubator-druid/pull/7133#discussion_r269841227
 
 

 ##########
 File path: docs/content/querying/scan-query.md
 ##########
 @@ -24,7 +24,16 @@ title: "Scan query"
 
 # Scan query
 
-Scan query returns raw Druid rows in streaming mode.
+The Scan query returns raw Druid rows in streaming mode.  The biggest 
difference between the Select query and the Scan
+query is that the Scan query does not retain all the returned rows in memory 
before they are returned to the client.  
+The Select query _will_ retain the rows in memory, causing memory pressure if 
too many rows are returned.  
+The Scan query can return all the rows without issuing another pagination 
query.
+
+In addition to straightforward usage where a Scan query is issued to the 
Broker, the Scan query can also be issued
 
 Review comment:
   In the time-ordering section, there's this line: "Also,
   time ordering is not support for queries issued directly to historicals 
unless a list of segments is specified." (don't mind the typo, I'll fix that 
right now).  Is that good enough?

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