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https://issues.apache.org/jira/browse/HIVE-17474?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16162657#comment-16162657
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liyunzhang_intel commented on HIVE-17474:
-----------------------------------------
the execution plan of hive on spark about DS/query70 is
[attached|https://issues.apache.org/jira/secure/attachment/12886590/explain.70.vec].
Investigate the problem, i found that several points
1. the statistics for sub-query is not correct, it estimates nearly 36g about
the result while actually the result is very small(nearly 30 rows about state
info). Because of this, the join between part1 and part2(see jira description)
is common join not map join. Maybe the calculation of statistics estimation
need be more intelligent in such complex sub-query.
{code}
Reducer 12
Reduce Operator Tree:
Select Operator
expressions: KEY.reducesinkkey0 (type: string),
KEY.reducesinkkey1 (type: double)
outputColumnNames: _col0, _col1
Statistics: Num rows: 4991930471 Data size: 109822470377 Basic
stats: COMPLETE Column stats: NONE
PTF Operator
Function definitions:
Input definition
input alias: ptf_0
output shape: _col0: string, _col1: double
type: WINDOWING
Windowing table definition
input alias: ptf_1
name: windowingtablefunction
order by: _col1 DESC NULLS LAST
partition by: _col0
raw input shape:
window functions:
window function definition
alias: rank_window_0
arguments: _col1
name: rank
window function: GenericUDAFRankEvaluator
window frame: PRECEDING(MAX)~FOLLOWING(MAX)
isPivotResult: true
Statistics: Num rows: 4991930471 Data size: 109822470377
Basic stats: COMPLETE Column stats: NONE
Filter Operator
predicate: (rank_window_0 <= 5) (type: boolean)
Statistics: Num rows: 1663976823 Data size: 36607490111
Basic stats: COMPLETE Column stats: NONE
Select Operator
expressions: _col0 (type: string)
outputColumnNames: _col0
Statistics: Num rows: 1663976823 Data size: 36607490111
Basic stats: COMPLETE Column stats: NONE
Reduce Output Operator
key expressions: _col0 (type: string)
sort order: +
Map-reduce partition columns: _col0 (type: string)
Statistics: Num rows: 1663976823 Data size: 36607490111
Basic stats: COMPLETE Column stats: NONE
{code}
> Poor Performance about subquery like DS/query70
> -----------------------------------------------
>
> Key: HIVE-17474
> URL: https://issues.apache.org/jira/browse/HIVE-17474
> Project: Hive
> Issue Type: Bug
> Reporter: liyunzhang_intel
> Attachments: explain.70.vec
>
>
> in
> [DS/query70|https://github.com/kellyzly/hive-testbench/blob/hive14/sample-queries-tpcds/query70.sql].
> {code}
> select
> sum(ss_net_profit) as total_sum
> ,s_state
> ,s_county
> ,grouping__id as lochierarchy
> , rank() over(partition by grouping__id, case when grouping__id == 2 then
> s_state end order by sum(ss_net_profit)) as rank_within_parent
> from
> store_sales ss join date_dim d1 on d1.d_date_sk = ss.ss_sold_date_sk
> join store s on s.s_store_sk = ss.ss_store_sk
> where
> d1.d_month_seq between 1193 and 1193+11
> and s.s_state in
> ( select s_state
> from (select s_state as s_state, sum(ss_net_profit),
> rank() over ( partition by s_state order by
> sum(ss_net_profit) desc) as ranking
> from store_sales, store, date_dim
> where d_month_seq between 1193 and 1193+11
> and date_dim.d_date_sk =
> store_sales.ss_sold_date_sk
> and store.s_store_sk = store_sales.ss_store_sk
> group by s_state
> ) tmp1
> where ranking <= 5
> )
> group by s_state,s_county with rollup
> order by
> lochierarchy desc
> ,case when lochierarchy = 0 then s_state end
> ,rank_within_parent
> limit 100;
> {code}
> let's analyze the query,
> part1: it calculates the sub-query and get the result of the state which
> ss_net_profit is less than 5.
> part2: big table store_sales join small tables date_dim, store and get the
> result.
> part3: part1 join part2
> the problem is on the part3, this is common join. The cardinality of part1
> and part2 is low as there are not very different values about states(
> actually there are 30 different values in the table store). If use common
> join, big data will go to the 30 reducers.
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