HyukjinKwon commented on a change in pull request #27616: [SPARK-30864]
[SQL]add the user guide for Adaptive Query Execution
URL: https://github.com/apache/spark/pull/27616#discussion_r390158893
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File path: docs/sql-performance-tuning.md
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@@ -186,3 +186,61 @@ The "REPARTITION_BY_RANGE" hint must have column names
and a partition number is
SELECT /*+ REPARTITION(3, c) */ * FROM t
SELECT /*+ REPARTITION_BY_RANGE(c) */ * FROM t
SELECT /*+ REPARTITION_BY_RANGE(3, c) */ * FROM t
+
+## Adaptive Query Execution
+Adaptive Query Execution (AQE) is an optimization technique in Spark SQL that
makes use of the runtime statistics to choose the most efficient query
execution plan. AQE is disabled by default. Spark SQL can use the umbrella
configuration of `spark.sql.adaptive.enabled` to control whether turn it
on/off. As of Spark 3.0, there are three major features in AQE, including
coalescing post-shuffle partitions, local shuffle reader optimization and
skewed join optimization.
+ ### Coalescing Post Shuffle Partition Number
Review comment:
There's a leading space here which should be removed. Also newline should be
inserted prior to '###'.
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