[GitHub] [spark] HyukjinKwon commented on a change in pull request #27616: [SPARK-30864] [SQL]add the user guide for Adaptive Query Execution

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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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