swuferhong commented on code in PR #20513:
URL: https://github.com/apache/flink/pull/20513#discussion_r948852444
##########
docs/content/docs/dev/table/sql/queries/hints.md:
##########
@@ -84,4 +84,205 @@ insert into kafka_table1 /*+
OPTIONS('sink.partitioner'='round-robin') */ select
```
+## Query Hints
+
+`Query Hints` specify that the indicated hints are used in the scope of a
query. They affect all operators in the statement.
+Now, Flink `Query Hints` support `Join Hints`.
+
+### Syntax
+The `Query Hints` syntax in Flink:
+```sql
+# Query Hints:
+SELECT /*+ hint [, hint ] */ ...
+
+hint:
+ hintName
+ | hintName '(' optionKey '=' optionVal [, optionKey '=' optionVal ]* ')'
+ | hintName '(' hintOption [, hintOption ]* ')'
+
+optionKey:
+ simpleIdentifier
+ | stringLiteral
+
+optionVal:
+ stringLiteral
+
+hintOption:
+ simpleIdentifier
+ | numericLiteral
+ | stringLiteral
+```
+
+### Join Hints
+
+Join hints allow users to suggest the join strategy to optimizer in order to
get a more optimal execution plan.
+Now Flink `Join Hints` support `BROADCAST`, `SHUFFLE_HASH`, `SHUFFLE_MERGE`
and `NEST_LOOP` Join Hints. Also, for same cases,
+`Join Hints` will conflict, we try to formulate the behavior of Join Hints for
these cases.
+
+#### BROADCAST Join Hints
Review Comment:
> `BROADCAST` or `BROADCAST Join Hint`
Done!
##########
docs/content/docs/dev/table/sql/queries/hints.md:
##########
@@ -84,4 +84,205 @@ insert into kafka_table1 /*+
OPTIONS('sink.partitioner'='round-robin') */ select
```
+## Query Hints
+
+`Query Hints` specify that the indicated hints are used in the scope of a
query. They affect all operators in the statement.
+Now, Flink `Query Hints` support `Join Hints`.
+
+### Syntax
+The `Query Hints` syntax in Flink:
+```sql
+# Query Hints:
+SELECT /*+ hint [, hint ] */ ...
+
+hint:
+ hintName
+ | hintName '(' optionKey '=' optionVal [, optionKey '=' optionVal ]* ')'
+ | hintName '(' hintOption [, hintOption ]* ')'
+
+optionKey:
+ simpleIdentifier
+ | stringLiteral
+
+optionVal:
+ stringLiteral
+
+hintOption:
+ simpleIdentifier
+ | numericLiteral
+ | stringLiteral
+```
+
+### Join Hints
+
+Join hints allow users to suggest the join strategy to optimizer in order to
get a more optimal execution plan.
+Now Flink `Join Hints` support `BROADCAST`, `SHUFFLE_HASH`, `SHUFFLE_MERGE`
and `NEST_LOOP` Join Hints. Also, for same cases,
+`Join Hints` will conflict, we try to formulate the behavior of Join Hints for
these cases.
+
+#### BROADCAST Join Hints
+
+{{< label Batch >}}
+
+For this type of `Join Hints`, suggests that join use `BroadCast join`
strategy. the join side with the hint will be broadcast to
+each downstream operator, and join side without hint will be sent directly to
the downstream operator with Forward.
+
+##### Examples
+
+*NOTE:* `BROADCAST Join Hints` only supports join with equivalence join
condition. And it doesn't support `Full Outer Join`.
+```sql
+CREATE TABLE t1 (id BIGINT, name STRING, age INT) WITH (...);
+CREATE TABLE t2 (id BIGINT, name STRING, age INT) WITH (...);
+CREATE TABLE t3 (id BIGINT, name STRING, age INT) WITH (...);
+
+-- Select t1 as join side with this hint, t1 will be the broadcast table.
+SELECT /*+ BROADCAST(t1) */ * FROM t1 JOIN t2 ON t1.id = t2.id;
+
+-- Select t1 and t3 as join side with this hint.
+-- For this case, when join between t1 and t2, t1 will be the broadcast table.
+-- And when join between the result after t1 joins t2 and t3, t3 will be the
broadcast table.
+SELECT /*+ BROADCAST(t1, t3) */ * FROM t1 JOIN t2 ON t1.id = t2.id JOIN t3 ON
t1.id = t3.id;
+
+-- BROADCAST Join Hints don't support non-equivalent join conditions.
+-- For this case, default join strategy will be adopted instead of BroadCast
join.
+SELECT /*+ BROADCAST(t1) */ * FROM t1 join t2 ON t1.id > t2.id;
+
+-- BROADCAST Join Hints strategy don't support full outer join.
+-- For this case, default join strategy will be adopted instead of BroadCast
join.
+SELECT /*+ BROADCAST(t1) */ * FROM t1 FULL OUTER JOIN t2 ON t1.id = t2.id;
+```
+
+#### SHUFFLE_HASH Join Hints
Review Comment:
> ditto
Done!
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