liyunzhang_intel created HIVE-17287:
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Summary: HoS can not deal with skewed data group by
Key: HIVE-17287
URL: https://issues.apache.org/jira/browse/HIVE-17287
Project: Hive
Issue Type: Bug
Reporter: liyunzhang_intel
In
[tpcds/query67.sql|https://github.com/kellyzly/hive-testbench/blob/hive14/sample-queries-tpcds/query67.sql],
fact table {{store_sales}} joins with small tables {{date_dim}},
{{item}},{{store}}. After join, groupby the intermediate data.
Here the data of {{store_sales}} on 3TB tpcds is skewed: there are 1824
partitions. The biggest partition is 25.7G and others are 715M.
{code}
hadoop fs -du -h
/user/hive/warehouse/tpcds_bin_partitioned_parquet_3000.db/store_sales
....
715.0 M
/user/hive/warehouse/tpcds_bin_partitioned_parquet_3000.db/store_sales/ss_sold_date_sk=2452639
713.9 M
/user/hive/warehouse/tpcds_bin_partitioned_parquet_3000.db/store_sales/ss_sold_date_sk=2452640
714.1 M
/user/hive/warehouse/tpcds_bin_partitioned_parquet_3000.db/store_sales/ss_sold_date_sk=2452641
712.9 M
/user/hive/warehouse/tpcds_bin_partitioned_parquet_3000.db/store_sales/ss_sold_date_sk=2452642
25.7 G
/user/hive/warehouse/tpcds_bin_partitioned_parquet_3000.db/store_sales/ss_sold_date_sk=__HIVE_DEFAULT_PARTITION__
{code}
The skewed table {{store_sales}} caused the failed job. Is there any way to
solve the groupby problem of skewed table? I tried to enable
{{hive.groupby.skewindata}} to first divide the data more evenly then start do
group by. But the job still hangs.
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