Yin Huai 962878843b [SPARK-11840][SQL] Restore the 1.5's behavior of planning a single distinct aggregation. ... The impact of this change is for a query that has a single distinct column and does not have any grouping expression like `SELECT COUNT(DISTINCT a) FROM table` The plan will be changed from ``` AGG-2 (count distinct) Shuffle to a single reducer Partial-AGG-2 (count distinct) AGG-1 (grouping on a) Shuffle by a Partial-AGG-1 (grouping on 1) ``` to the following one (1.5 uses this) ``` AGG-2 AGG-1 (grouping on a) Shuffle to a single reducer Partial-AGG-1(grouping on a) ``` The first plan is more robust. However, to better benchmark the impact of this change, we should use 1.5's plan and use the conf of `spark.sql.specializeSingleDistinctAggPlanning` to control the plan. Author: Yin Huai <yhuai@databricks.com> Closes #9828 from yhuai/distinctRewriter.		2015-11-19 11:02:17 -08:00
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src	[SPARK-11840][SQL] Restore the 1.5's behavior of planning a single distinct aggregation.	2015-11-19 11:02:17 -08:00
pom.xml	[SPARK-10300] [BUILD] [TESTS] Add support for test tags in run-tests.py.	2015-10-07 14:11:21 -07:00