Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/19714#discussion_r153677941
--- Diff: docs/sql-programming-guide.md ---
@@ -1492,6 +1492,61 @@ 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.
+Spark Broadcast Hint has higher priority than autoBroadcastJoin mechanism,
examples:
+
+<div class="codetabs">
+
+<div data-lang="scala" markdown="1">
+
+{% highlight scala %}
+val src = sql("SELECT * FROM src")
+broadcast(src).join(recordsDF, Seq("key")).show()
--- End diff --
a more standard way:
```
import org.apache.spark.sql.functions.broadcast
broadcast(spark.table("src")).join(spark.table("records"),
Seq("key")).show()
```
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