Yin Huai e3355090d4 [SPARK-10143] [SQL] Use parquet's block size (row group size) setting as the min split size if necessary. ... https://issues.apache.org/jira/browse/SPARK-10143 With this PR, we will set min split size to parquet's block size (row group size) set in the conf if the min split size is smaller. So, we can avoid have too many tasks and even useless tasks for reading parquet data. I tested it locally. The table I have has 343MB and it is in my local FS. Because I did not set any min/max split size, the default split size was 32MB and the map stage had 11 tasks. But there were only three tasks that actually read data. With my PR, there were only three tasks in the map stage. Here is the difference. Without this PR:  With this PR:  Even if the block size setting does match the actual block size of parquet file, I think it is still generally good to use parquet's block size setting if min split size is smaller than this block size. Tested it on a cluster using ``` val count = sqlContext.table("""store_sales""").groupBy().count().queryExecution.executedPlan(3).execute().count ``` Basically, it reads 0 column of table `store_sales`. My table has 1824 parquet files with size from 80MB to 280MB (1 to 3 row group sizes). Without this patch, in a 16 worker cluster, the job had 5023 tasks and spent 102s. With this patch, the job had 2893 tasks and spent 64s. It is still not as good as using one mapper per file (1824 tasks and 42s), but it is much better than our master. Author: Yin Huai <yhuai@databricks.com> Closes #8346 from yhuai/parquetMinSplit.		2015-08-21 14:30:00 -07:00
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main	[SPARK-10143] [SQL] Use parquet's block size (row group size) setting as the min split size if necessary.	2015-08-21 14:30:00 -07:00
test	[SPARK-10130] [SQL] type coercion for IF should have children resolved first	2015-08-21 12:21:51 -07:00