Steve Ebersole commented on HHH-2448:
Guys, it is not quite so easy. In order for the DB to know that an incoming query only
differs from any other query based on the defined return aliases, the DB would need to
perform at least some degree of lexical analysis on that incoming query. At the very
least that lexical analysis would be needed to determine the overal structure and identify
the tokens which are aliases. So where is that fulcrum? This is exactly why we do not
cache criteria query plans, and our caching of HQL query plans has this same exact
And really, is this a requirement for the underlying DB? This is something Hibernate
could be made to do.
However, this is obviously fairly low on my radar ;)
Generate identical column aliases among cluster
Components: query-hql, query-criteria
Environment: Hibernate version: 3.2.2, 2.1.8
Database: Oracle 188.8.131.52
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
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
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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