Github user wzhfy commented on a diff in the pull request:
https://github.com/apache/spark/pull/19714#discussion_r153969298
--- Diff: docs/sql-programming-guide.md ---
@@ -1492,6 +1492,64 @@ that these options will be deprecated in future
release as more optimizations ar
</tr>
</table>
+## Broadcast Hint for SQL Queries
+
+The `BROADCAST` hint guides Spark to broadcast each specified table when
joining them with another table or view.
+When Spark deciding the join methods, the broadcast hash join (i.e., BHJ)
is preferred,
+even if the statistics is above the configuration
`spark.sql.autoBroadcastJoinThreshold`.
+When both sides of a join are specified, Spark broadcasts the one having
the lower statistics.
+Note Spark does not guaranttee BHJ is always chosen, since not all cases
(e.g. full outer join)
--- End diff --
typo: guarantee
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