In regards to http://opensource.atlassian.com/projects/hibernate/browse/HHH-3579 I am trying to put together the best all around support for java.util.UUID we can as a type.
Obviously most databases "support uuid" via char/varchar data type. Postgresql being the lone exception of which I am aware with their special UUID datatype, even though they choose to map it to java.sql.Types.OTHER (don't get me started). So for sure we can support UUID in every database. The next logical thought was supporting UUID as an identifier value. If we were to add that what I would really prefer is a way to obtain the UUID ahead of time (pre-insert) which would mean knowing what databases supported a UUID-generation function and, for those that did, what that function is. For those that do not, is using java.util.UUID.randomUUID() a viable alternative? A list of major databases and their support/non-support for generating UUID values that I know of are as follows: 1) postgresql - database itself does not support generation, instead relying on an optional module called uuid-ossp 2) mysql - supports generation via the UUID() function 3) h2 - supports generation via the RANDOM_UUID() 4) hsqldb - does not support generation afaict 5) derby - does not support generation afaict 6) db2 - does have a GENERATE_UNIQUE() function; was not able to tell if that is compatible with java.util.UUID 7) firebird - supports generation via GEN_UUID() 8) informix - does not support generation afaict 9) ingres - supports via UUID_CREATE() 10) oracle - supports via SYS_GUID() 11) maxdb (sapdb) - does not support generation afaict 12) mssql (sql server) - does have a NEWID() function, though it generates a string with hyphons in it; not sure how/if this value relates to java.util.UUID 13) sybase - like mssql also has a NEWID() function which here can additionally be given a parameter to say whether to include hyphons etc; again, not sure how/if this value relates to java.util.UUID 14) terradata - does not support generation afaict DISCLAIMER : When I say "does not support" I mean in the base server install. As I pointed out with postgresql I understand some might have additional optional or third-party modules that add such capabilities So by my count, that means that we can have pretty complete support for UUID on the following databases without any extra requirements: a) mysql b) h2 c) firebird d) ingres e) oracle Databases with potential support: a) postgresql - is it reasonable to require this uuid-ossp module? b) db2 - what is the compatibility of its GENERATE_UNIQUE() function with java.util.UUID? c) mssql/sybase - what is the compatibility of NEWID() function with with java.util.UUID? For databases which do not support UUID generation, the question becomes how do we support that in hibernate for identifiers? Do we rely on java.util.UUID.randomUUID()? Do you use a special generator like http://jug.safehaus.org/ ? Other options? Also, if anyone notices issues in my db support investigations please let me know. -- Steve Ebersole <st...@hibernate.org> http://hibernate.org _______________________________________________ hibernate-dev mailing list hibernate-dev@lists.jboss.org https://lists.jboss.org/mailman/listinfo/hibernate-dev
