Help Center/ MapReduce Service/ User Guide (Kuala Lumpur Region)/ MRS Cluster Component Operation Gudie/ Using Spark2x/ Spark2x Performance Tuning/ Spark SQL and DataFrame Tuning/ Optimizing the Aggregate Algorithms

Updated on 2022-08-12 GMT+08:00

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Optimizing the Aggregate Algorithms

Scenario

Spark SQL supports hash aggregate algorithm. Namely, use fast aggregate hashmap as cache to improve aggregate performance. The hashmap replaces the previous ColumnarBatch to avoid performance problems caused by the wide mode (multiple key or value fields) of an aggregate table.

Procedure

If you want to enable optimization of aggregate algorithm, configure following parameters in the spark-defaults.conf file on the Spark client.

**Table 1** Parameter description
Parameter	Description	Default Value
spark.sql.codegen.aggregate.map.twolevel.enabled	Specifies whether to enable aggregation algorithm optimization. true: Enable false: Disable	true

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