huaxingao commented on a change in pull request #28672:
URL: https://github.com/apache/spark/pull/28672#discussion_r432798521
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File path: docs/sql-ref-syntax-qry-select-hints.md
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@@ -21,14 +21,86 @@ license: |
### Description
-Join Hints allow users to suggest the join strategy that Spark should use.
Prior to Spark 3.0, only the `BROADCAST` Join Hint was supported. `MERGE`,
`SHUFFLE_HASH` and `SHUFFLE_REPLICATE_NL` Joint Hints support was added in 3.0.
When different join strategy hints are specified on both sides of a join, Spark
prioritizes hints in the following order: `BROADCAST` over `MERGE` over
`SHUFFLE_HASH` over `SHUFFLE_REPLICATE_NL`. When both sides are specified with
the `BROADCAST` hint or the `SHUFFLE_HASH` hint, Spark will pick the build side
based on the join type and the sizes of the relations. Since a given strategy
may not support all join types, Spark is not guaranteed to use the join
strategy suggested by the hint.
+Hints give users a way to suggest how Spark SQL to use specific approaches to
generate its execution plan.
### Syntax
```sql
-/*+ join_hint [ , ... ] */
+/*+ hint [ , ... ] */
```
+### Partitioning Hints
+
+Partitioning hints allow users to suggest a partitioning stragety that Spark
should follow. `COALESCE`, `REPARTITION`,
+and `REPARTITION_BY_RANGE` hints are supported and are equivalent to
`coalesce`, `repartition`, and
+`repartitionByRange` [Dataset
APIs](api/scala/org/apache/spark/sql/Dataset.html), respectively. These hints
give users
+a way to tune performance and control the number of output files in Spark SQL.
When multiple partitioning hints are
+specified, multiple nodes are inserted into the logical plan, but the leftmost
hint is picked by the optimizer.
Review comment:
Thanks for your comment. I will keep the one in description.
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