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Comment: mention changed default of hive.auto.convert.join with link to HIVE-3297

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No Format
set hive.auto.convert.join=true;
select count(*) from
store_sales join time_dim on (ss_sold_time_sk = t_time_sk)

The default value for hive.auto.convert.join was false in Hive 0.10.0.  Hive 0.11.0 changed the default to true (HIVE-3297).

MAPJOINs are processed by loading the smaller table into an in-memory hash map and matching keys with the larger table as they are streamed through. The prior implementation has this division of labor:

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