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

[Loïc LEFEVRE (JIRA)]

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

  Components: query-sql  
    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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