[Hibernate-JIRA] Created: (HHH-2448) Generate identical column aliases among cluster
by 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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11 years, 10 months
[Hibernate-JIRA] Created: (HHH-3811) Bug: No ability to escape SQL keywords in HQL queries.
by John Roberts (JIRA)
Bug: No ability to escape SQL keywords in HQL queries.
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Key: HHH-3811
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3811
Project: Hibernate Core
Issue Type: Bug
Components: core
Affects Versions: 3.3.0.CR1
Environment: 3.3.0.CR1, MS SQL Server 2005 Express
Reporter: John Roberts
Priority: Critical
There appears to be no way to escape property names that are SQL keywords in HQL queries. For example, if you have a property named "key", which is a reasonable name for a property, and you are constructing an HQL query, e.g.:
session.createQuery("select from Entities where key=?");
That will fail on MS SQL Server, because "key" is a reserved T-SQL keyword. However, there is no way to make it succeed, as either an absent-minded developer appears to have forgotten to add the ability to escape keywords to HQL (oops), or it's the secret of the millennium and was left out of the documentation on purpose (it has certainly boggled the minds of the folks on FreeNode #java, #hibernate, and the hibernate forum). Note that none of the following will succeed (this is what I have tried so far):
session.createQuery("select from Entities where key=?");
session.createQuery("select from Entities where [key]=?"); // <-- mssql style still fails to be parsed
session.createQuery("select from Entities where `key`=?");
session.createQuery("select from Entities where 'key'=?");
session.createQuery("select from Entities where \"key\"=?");
session.createQuery("select from Entities where ''key''=?");
session.createQuery("select from Entities where {key}=?");
session.createQuery("select from Entities where <key>=?");
session.createQuery("select from Entities where (key)=?");
session.createQuery("select from Entities where $key$=?");
session.createQuery("select from Entities where $key=?");
Note that using the underlying DBMS's escape method *does* work for column names in the entity mappings, but does not work in actual HQL.
Since most DBMS's have their own dialects of SQL, the inability to escape keywords in HQL means that it is generally impossible to guarantee that any given HQL query will work unless you specifically design your application around the underlying DBMS (which is precisely one of the things you were hoping to avoid with Hibernate -- although on the other hand you're already tied to the DBMS with escaped keywords in the entity mapping anyways).
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11 years, 10 months
[Hibernate-JIRA] Created: (HHH-3818) Hibernate/JBC integration doesn't property handle Entity/CollectionRegionAccessStrategy evict
by Brian Stansberry (JIRA)
Hibernate/JBC integration doesn't property handle Entity/CollectionRegionAccessStrategy evict
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Key: HHH-3818
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3818
Project: Hibernate Core
Issue Type: Bug
Components: caching (L2)
Affects Versions: 3.3.1
Reporter: Brian Stansberry
Assignee: Brian Stansberry
Fix For: 3.3.x
EntityRegionAccessStrategy and CollectionRegionAccessStrategy have evict(Object key) and evictAll() that say they must cause removal of items from the cache "immediately without regard for transaction isolation." The Hibernate/JBC integration is not properly handling this as the JBC removeNode calls it makes are not dealing with transactional issues. The integration needs to:
1) Perhaps suspend any ongoing tx (particularly since these calls are typically made from a tx Synchronization's afterCompletion() callback, when the tx is Status.COMMITTED and it isn't appropriate to call into the cache expecting the cache to incorporate the call into the transaction. (Alhthough I believe JBC handles this correctly by ignoring the tx, since it isn't ACTIVE).
2) Deal with the fact that the tx that is being committed is likely holding locks in JBC. This is the big issue. I believe dealing with this will a) require keeping state in the Hib/JBC integration layer's Region to track that an eviction has occurred but may not be reflected in JBC b) using JBC as a notification bus to propagate the fact of the eviction to other nodes c) attempting to evict the data from JBC locally, failing promptly in the face of lock conflicts d) including in any get() or putFromLoad() calls logic to check the state from a), again attempting to evict locally (with a very short timeout) if not yet evicted and not allowing calls to proceed into JBC until successful.
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11 years, 10 months
[Hibernate-JIRA] Created: (HHH-4857) Sharing some of the config info from Ejb3Configuration and SessionFactoryImpl
by Chris Baxter (JIRA)
Sharing some of the config info from Ejb3Configuration and SessionFactoryImpl
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Key: HHH-4857
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-4857
Project: Hibernate Core
Issue Type: New Feature
Components: core, entity-manager
Reporter: Chris Baxter
Priority: Minor
In our system, we have each clients data in a separate DB instance. We're using JPA (via hibernate) on top of that to get at the data. The problem here is that for each client DB supported by one of our jboss servers, we have to have an instance of EntityManagerFactory compete with an Ejb3Configuration instance. Each config instance takes up around 20 MBs of permanent space, so if we have have 1000 client DBs supported by a jboss instance, it takes up a hugh amount of memory for information that will always be the same (the DB schemas are always the exact same in each client DB) across all EntityManagerFactory instances. So what I want to know is if there is a way to only have one instance of Ejb3Configuration that can be shared across all of the EntityManagerFactory instances that are spawning my EntityManagers. This would be huge as it would help me save many gigs of memory that never can be collected (old gen in jboss).
I prototyped some changes locally to Ejb3Configuration (to allow an instance of AnnotationConfiguration to be supplied in the constructor, allowing sharing across all instanced of this class) and to SessionFactoryImpl (to share some of the properties like entityPersisters, classMetadata and such) and I was able to reduce the footprint to 20 MBs for the first DB and then under a MB for each additional DB. The changes I made were a bit quick and dirty though, just to see if it was possible. So I'm taking out this feature request to see if this is a piece of work that you guys can do (or I can contribute after refactoring to a more suitable approach) and integrate into the main code for hibernate-core and hibernate-entitymanager. Let me know if this is something you guys think to be a valuable addition.
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11 years, 11 months
[Hibernate-JIRA] Created: (HHH-3465) HiRDB Support
by Tomoto Shimizu Washio (JIRA)
HiRDB Support
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Key: HHH-3465
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3465
Project: Hibernate3
Issue Type: New Feature
Components: core
Affects Versions: 3.2.5
Environment: 3.2.5 + HiRDB V8 + Type4 JDBC Driver
Reporter: Tomoto Shimizu Washio
Attachments: hirdbdialect.patch
I would like to contribute with a dialect for HiRDB, Hitachi's RDBMS.
(For more information, please see http://www.hitachi.co.jp/Prod/comp/soft1/global/prod/hirdb/)
I added 4 classes and slightly modified 2 existing classes as shown below. Please look at the documentation at the top of the patch for explanations.
org.hibernate.dialect.HiRDBDialect (added)
org.hibernate.dialect.UserFuncDeclParser (added)
org.hibernate.dialect.DialectFactory (modified)
org.hibernate.dialect.function.AnsiTrimEmulationFunction (modified)
org.hibernate.dialect.function.AnsiTrimEmulationFunctionWithTrimstrs (added)
org.hibernate.dialect.function.TypeQualifiedSQLFunction (added)
You may think this code is relatively large as a dialect. It is because I also implemented user-defined function support. As HiRDB requires '?' parameters to be qualified by 'as <type>' in user-defined function invocations, I made a parser for the type declarations that the user specified in the properties file, and a renderer for the type qualifier. See javadoc comments of HiRDBDialect and UserFuncDeclParser for more details.
This patch is created on Hibernate 3.2.5.ga and tested on HiRDB V8 with Type4 JDBC Driver. The example configuration for HiRDB is shown below:
hibernate.dialect org.hibernate.dialect.HiRDBDialect
hibernate.connection.driver_class JP.co.Hitachi.soft.HiRDB.JDBC.HiRDBDriver
hibernate.connection.url jdbc:hitachi:hirdb://DBID=@HIRDBENVGRP=C:/hirdb.ini
hibernate.connection.username hitachi
hibernate.connection.password hitachi
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11 years, 11 months