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Posted to issues-all@impala.apache.org by "Joe McDonnell (JIRA)" <ji...@apache.org> on 2019/06/11 00:32:00 UTC
[jira] [Updated] (IMPALA-8630) Consistent remote placement should
include partition information when calculating placement
[ https://issues.apache.org/jira/browse/IMPALA-8630?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Joe McDonnell updated IMPALA-8630:
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Summary: Consistent remote placement should include partition information when calculating placement (was: Consistent remote placement should include partition id when calculating placement)
> Consistent remote placement should include partition information when calculating placement
> -------------------------------------------------------------------------------------------
>
> Key: IMPALA-8630
> URL: https://issues.apache.org/jira/browse/IMPALA-8630
> Project: IMPALA
> Issue Type: Bug
> Components: Backend
> Affects Versions: Impala 3.2.0
> Reporter: Joe McDonnell
> Assignee: Joe McDonnell
> Priority: Blocker
>
> For partitioned tables, the actual filenames within partitions may not have large entropy. Impala includes information in its filenames that would not be the same across partitions, but this is common for tables written by the current CDH version of Hive. For example, in our minicluster, the TPC-DS store_sales table has many partitions, but the actual filenames within partitions are very simple:
> {noformat}
> hdfs dfs -ls /test-warehouse/tpcds.store_sales/ss_sold_date_sk=2452642
> Found 1 items
> -rwxr-xr-x 3 joe supergroup 379535 2019-06-05 15:16 /test-warehouse/tpcds.store_sales/ss_sold_date_sk=2452642/000000_0
> hdfs dfs -ls /test-warehouse/tpcds.store_sales/ss_sold_date_sk=2452640
> Found 1 items
> -rwxr-xr-x 3 joe supergroup 412959 2019-06-05 15:16 /test-warehouse/tpcds.store_sales/ss_sold_date_sk=2452640/000000_0{noformat}
> Right now, consistent remote placement uses the filename+offset without the partition id.
> {code:java}
> uint32_t hash = HashUtil::Hash(hdfs_file_split->relative_path.data(),
> hdfs_file_split->relative_path.length(), 0);
> {code}
> This would produce a poor balance of files across nodes when there is low entropy in filenames. This should be amended to include the partition id, which is already accessible on the THdfsFileSplit.
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