Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/19714#discussion_r153427238
--- Diff: docs/sql-programming-guide.md ---
@@ -1492,6 +1492,19 @@ that these options will be deprecated in future
release as more optimizations ar
</tr>
</table>
+## Broadcast Hint for SQL Queries
+
+Broadcast hint is a way for users to manually annotate a query and suggest
to the query optimizer the join method.
+It is very useful when the query optimizer cannot make optimal decision
with respect to join methods
+due to conservativeness or the lack of proper statistics. The hint syntax
looks like the following
+(Note that we accept `BROADCAST`, `BROADCASTJOIN` and `MAPJOIN` for
broadcast hint):
+
+{% highlight sql %}
+
+SELECT /*+ MAPJOIN(t1) */ * FROM t1 JOIN t2 ON t1.key = t2.key
--- End diff --
let's use `BROADCAST` instead of `MAPJOIN` in the example
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