Re: [eclipselink-users] Hibernate ID Migration
Both sequence objects and table sequencing are generated on the database.
Sequence objects (supported in Oracle and a few other databases) allow
preallocation so have very good performance and do not have any
synchronization issues, as they are allocated outside of the transaction
Table sequencing also supports a preallocation size, and TopLink can
allocate sequence numbers outside the transaction context (sequence
connection pool) so does not have any synchronization issues (especially if
a large preallocation size is used).
Not using a sequence preallocation size, or using identity sequencing will
lead to poor performance, and can lead to synchronization issues with table
sequencing. But also long as you use a large sequence preallocation size
there are no issues.
Frans Thamura-2 wrote:
>> EclipseLink (and JPA) do not have a UUID generator, you could implement
>> own through subclassing the Sequence class
>> (org.eclipse.persistence.sequencing) (and perhaps contribute it to
>> EclipseLink), but I would recommend you use one of the standard id
> i dont get it.
> we use the UUID because we have bad experience with PrimaryKey
> Implementation esp for sync mechanism.
> is the table sequence directlyfrom database or like hibernate's UUID
http://wiki.eclipse.org/User:James.sutherland.oracle.com James Sutherland
EclipseLink , http://www.oracle.com/technology/products/ias/toplink/
Wiki: http://wiki.eclipse.org/EclipseLink EclipseLink ,
Forums: http://forums.oracle.com/forums/forum.jspa?forumID=48 TopLink ,
Book: http://en.wikibooks.org/wiki/Java_Persistence Java Persistence
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