[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-2448) Generate identical column aliases among cluster

[Loïc LEFEVRE (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-2448?page=comments#action_26313 ] 

Loïc LEFEVRE commented on HHH-2448:
-----------------------------------

The problem, is we don't use annotations and we are using JDK 1.4.2.

About the "should be able to merge" part, it is not possible, the text of SQL queries stored in the SGA are accessible:
- either in v$sql (first 1000 chars),
- either in v$sqltext (or v$sqltext_with_newlines) by chunks of 64 chars

Merging statistics of queries bypassing the column aliases would mean rewriting in SQL an SQL parser... 


> Generate identical column aliases among cluster
> -----------------------------------------------
>
>          Key: HHH-2448
>          URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2448
>      Project: Hibernate3
>         Type: Improvement

>   Components: query-hql, query-criteria
>     Versions: 3.2.2
>  Environment: Hibernate version: 3.2.2, 2.1.8
> Database: Oracle 9.2.0.8
>     Reporter: Loïc LEFEVRE
>  Attachments: report_1.txt, report_2.txt
>
>
> Among our weblogic cluster (12 instances), we can see that a query can have different column aliases.
> Although all seems correct, when regarding database reports like StatsPack or Spotlight we can see that because of these different aliases, the reports are wrong. Indeed, a resource consuming query can see its associated report properties (cpu usage, buffer gets, number of executions...) divided by the number of weblogic instances of our cluster (i.e. divided by 12) thus preventing us to pinpoint the queries to look at.
> On a 3 instances cluster, we can see this report:
> REPORT#1: one statement with a poor number of buffer gets/execution is reported splitted in 3, see the alias generated for column DTO.CREATION_DATE
> for example
> On a 4 instances cluster, we can see this report:
> REPORT#2: one statement responsible of the latch free/cache buffers chains wait events splitted in 4, note the column alias generated fordeffcashcy0_.BEST_EXPECTED_CY
> More than confusing the DBAs about the same query with n different "faces", our reports don't show us all the queries to look at: indeed, in our "Top 50 queries", a lot of them are duplicates! Also the memory required in the SGA to store the queries, the execution plan and so on is increased...
> Finally, although the column aliases can have up to 30 characters under Oracle, the limit is set to 10, why? 

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