[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-3011) merge() optimization for Oracle dialect
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http://opensource.atlassian.com/projects/hibernate/browse/HHH-3011?page=c...
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Yves Galante commented on HHH-3011:
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I think if you use "unsaved-value" parameter on field ID,VERSION or TIMESTAMPS,
hibernate will not generate an SELECT when you call session.merge or
session.saveorupdate.
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Hibernate doc (5.1.4.5)
"Choosing the assigned generator makes Hibernate use
unsaved-value="undefined", forcing Hibernate to go to the database to determine
if an instance is transient or detached, unless there is a version or timestamp property,
or you define Interceptor.isUnsaved()."
merge() optimization for Oracle dialect
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Key: HHH-3011
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3011
Project: Hibernate3
Issue Type: Improvement
Components: core
Reporter: MG
Priority: Minor
merge() optimization for Oracle dialect.
Since 9i Oracle has a MERGE statement which is very useful to save round trips to
database in merge() call
which will make dramatic improvement for performance of loading large row sets.
MERGE command processes the conditional INSERT-or-UPDATE within a single statement.
So instead of doing 'select' first to detect whether entity is in database or not
(This is one round trip to DB)
and then issuing 'update' or 'insert' all of it could be done in one
statement with no extra round trips using oracle SQL MERGE statement.
http://www.oracle.com/technology/products/oracle9i/daily/Aug24.html
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