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https://issues.apache.org/jira/browse/HIVE-1342?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ted Xu updated HIVE-1342:
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Attachment: ppd_same_alias_2.patch
Hi John,
Thank you for reviewing the patch. I updated the patch to solve HIVE-1395.
I dig into the code and find that the same alias in different subqueries can be
ambiguous only if PPD is parsing CommonJoinOperator, so I just add some special
case in PPD for CommonJoinOperator.
As you mentioned above, adding namespace to RowResolver or OpParseContext can
also fix it, but I think we better keep their implementation simple.
> Predicate push down get error result when sub-queries have the same alias
> name
> -------------------------------------------------------------------------------
>
> Key: HIVE-1342
> URL: https://issues.apache.org/jira/browse/HIVE-1342
> Project: Hadoop Hive
> Issue Type: Bug
> Components: Query Processor
> Affects Versions: 0.6.0
> Reporter: Ted Xu
> Assignee: Ted Xu
> Priority: Critical
> Fix For: 0.6.0
>
> Attachments: cmd.hql, explain, ppd_same_alias_1.patch,
> ppd_same_alias_2.patch
>
>
> Query is over-optimized by PPD when sub-queries have the same alias name, see
> the query:
> -------------------------------
> create table if not exists dm_fact_buyer_prd_info_d (
> category_id string
> ,gmv_trade_num int
> ,user_id int
> )
> PARTITIONED BY (ds int);
> set hive.optimize.ppd=true;
> set hive.map.aggr=true;
> explain select category_id1,category_id2,assoc_idx
> from (
> select
> category_id1
> , category_id2
> , count(distinct user_id) as assoc_idx
> from (
> select
> t1.category_id as category_id1
> , t2.category_id as category_id2
> , t1.user_id
> from (
> select category_id, user_id
> from dm_fact_buyer_prd_info_d
> group by category_id, user_id ) t1
> join (
> select category_id, user_id
> from dm_fact_buyer_prd_info_d
> group by category_id, user_id ) t2 on
> t1.user_id=t2.user_id
> ) t1
> group by category_id1, category_id2 ) t_o
> where category_id1 <> category_id2
> and assoc_idx > 2;
> -----------------------------
> The query above will fail when execute, throwing exception: "can not cast
> UDFOpNotEqual(Text, IntWritable) to UDFOpNotEqual(Text, Text)".
> I explained the query and the execute plan looks really wired ( only Stage-1,
> see the highlighted predicate):
> -------------------------------
> Stage: Stage-1
> Map Reduce
> Alias -> Map Operator Tree:
> t_o:t1:t1:dm_fact_buyer_prd_info_d
> TableScan
> alias: dm_fact_buyer_prd_info_d
> Filter Operator
> predicate:
> expr: *(category_id <> user_id)*
> type: boolean
> Select Operator
> expressions:
> expr: category_id
> type: string
> expr: user_id
> type: bigint
> outputColumnNames: category_id, user_id
> Group By Operator
> keys:
> expr: category_id
> type: string
> expr: user_id
> type: bigint
> mode: hash
> outputColumnNames: _col0, _col1
> Reduce Output Operator
> key expressions:
> expr: _col0
> type: string
> expr: _col1
> type: bigint
> sort order: ++
> Map-reduce partition columns:
> expr: _col0
> type: string
> expr: _col1
> type: bigint
> tag: -1
> Reduce Operator Tree:
> Group By Operator
> keys:
> expr: KEY._col0
> type: string
> expr: KEY._col1
> type: bigint
> mode: mergepartial
> outputColumnNames: _col0, _col1
> Select Operator
> expressions:
> expr: _col0
> type: string
> expr: _col1
> type: bigint
> outputColumnNames: _col0, _col1
> File Output Operator
> compressed: true
> GlobalTableId: 0
> table:
> input format:
> org.apache.hadoop.mapred.SequenceFileInputFormat
> output format:
> org.apache.hadoop.hive.ql.io.HiveSequenceFileOutputFormat
> ----------------------------------
> If disabling predicate push down (set hive.optimize.ppd=true), the error is
> gone; I tried disabling map side aggregate, the error is gone,too.
> *Changing the alias of subquery 't1' (either the inner one or the join
> result), the bug disappears, too.*
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