當hibernate的hbm2dll配置為
- hibernate.hbm2ddl.auto update
將會發現Hibernate不會為我們創建任何自定義的索引(不包括主鍵跟外鍵索引),不論你使用xml方式或者annotation進行聲明配置
這個問題在Hibernate的JIRA多次出現，甚至有人專門為此發布了打了補丁的hibernate.jar
這個所謂的bug，在目前已發布的hibernate的版本中，一直都沒有解決，或者說不予理睬(Gavin King個人認為這個不是bug)
這里引用hibernate 3.2.5版的jira
http://opensource.atlassian.com/projects/hibernate/browse/HHH-1012
引用Hibernate上官方的解釋
引用
The hibernate.hbm2ddl.auto=update setting doesn't create indexes
SchemaUpdate is activated by this configuration setting. SchemaUpdate is not really very powerful and comes without any warranties. For example, it does not create any indexes automatically. Furthermore, SchemaUpdate is only useful in development, per definition (a production schema is never updated automatically). You don't need indexes in development.
Hibernate doesn't generate the database indexes I want in the schema!
Automatic schema export (and update) by Hibernate tools is only useful in development. You never need indexes in development, they are purely for performance and scalability tuning in production systems. Production schemas are never automatically generated, at least not completely. A DBA adds indexes to the automatically generated schema during SQL tuning and testing of the application, before going into production with the (possibly automatically generated) base schema, and her handwritten optimized DDL. Also note that optimized DDL is highly vendor specific and totally dependent on the environment (SQL execution plans, tablespace configuration, caches, etc). Even if Hibernate developers would encourage you to automatically generate production-ready schemas (we don't, and we also don't like ad-hoc SQL tuning by throwing a bunch of indexes onto a schema), Hibernate could never offer such a feature.