[SPARK-6548] stddev_pop and stddev_samp aggregate functions

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.6.0
• Component/s: SQL
• Labels: DataFrame starter
• Target Version/s: 1.6.0
• Assignee: Jihong Ma
• Reporter: Reynold Xin
• Shepherd: Michael Armbrust
• Created: 26/Mar/15 08:02
• Updated: 14/Sep/15 18:28
• Resolved: 12/Sep/15 17:17

Description

Add it to the list of aggregate functions:

https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/functions.scala

Also add it to

https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/GroupedData.scala

We can either add a Stddev Catalyst expression, or just compute it using existing functions like here: https://github.com/apache/spark/commit/5bbcd1304cfebba31ec6857a80d3825a40d02e83#diff-c3d0394b2fc08fb2842ff0362a5ac6c9R776

Issue Links

• is blocked by: SPARK-8800 Spark SQL Decimal Division operation loss of precision/scale when type is defined as DecimalType.Unlimited
• links to: [Github] Pull Request #5228 (dreamquster)
• links to: [Github] Pull Request #5357 (dreamquster)
• links to: [Github] Pull Request #6297 (JihongMA)