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https://issues.apache.org/jira/browse/HIVE-16602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16172918#comment-16172918
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liyunzhang_intel commented on HIVE-16602:
-----------------------------------------
[~jcamachorodriguez]: thanks for your reply.
{quote}
...it appears multiple times in the query.
{quote}
i mean the ts is used in the query for more than once. so shared scan
optimization will work. I test this in 10g scale in DS queries like
[query7|https://github.com/hortonworks/hive-testbench/blob/hive14/sample-queries-tpcds/query17.sql],[query70
|https://github.com/hortonworks/hive-testbench/blob/hive14/sample-queries-tpcds/query70.sql
] on 10g scale. But not see big improvement. I guess the reason maybe the
data scale is small so that not too much time is reduced even though less TS is
called.
||query||Before HIVE-16602||HIVE-16602||
|query7 |53.677s|51.934s |
|query70 |46.951s| 47.48s|
> Implement shared scans with Tez
> -------------------------------
>
> Key: HIVE-16602
> URL: https://issues.apache.org/jira/browse/HIVE-16602
> Project: Hive
> Issue Type: New Feature
> Components: Physical Optimizer
> Affects Versions: 3.0.0
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
> Labels: TODOC3.0
> Fix For: 3.0.0
>
> Attachments: HIVE-16602.01.patch, HIVE-16602.02.patch,
> HIVE-16602.03.patch, HIVE-16602.04.patch, HIVE-16602.patch
>
>
> Given a query plan, the goal is to identify scans on input tables that can be
> merged so the data is read only once. Optimization will be carried out at the
> physical level.
> In the longer term, identification of equivalent expressions and
> reutilization of intermediary results should be done at the logical layer via
> Spool operator.
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