Re: [xwiki-users] Using XWiki in other databases than MySQL

Reporting, out of my mind of months ago, for Oracle - First, oracle does assume an empty string same as null, this has 2 majors implications * The 'not null' String elements can get nulled when stored on database, triggering lots of hibernate exception when they are retrieved again. The 'not null' should be removed from String and all string getters in the bean should do something like return (value==null?"":value). Only exception to this should be keys, but keys can not be empty strings either. Oracle 10, i think is supposed to have this problem fixed and nulls are no more same a empty strings. However, oracle 9 here. * Another point, in sql, any boolean expression which implies a null is systematically evaluated to 'false'. As a result, the SQL query expression ":var1 not equal :var2 " is always evaluated to false if any of :var1 or :var2 is an empty string on oracle. A workaround at that time was to hunt expressions involving non key Strings and replace them with more complex expression taking into account null cases - Oracle is quite limited in the way it handles muliple lobs column in the same table. The hibernate mapping of xwiki uses String of length > 4096, this is converted to the type "TEXT" in oracle language. A TEXT has nearly the same behaviour as a varchar in oracle, meaning it can be used as a string in expression. However, there can be only one TEXT field per row. When there were several String of length >4096 in hibernate, they were all blindly converted to oracle TEXT type. The database of course refused to create such tables. Another alternative is clob (Character Large Object), you can have several on same row, however they do not act like varchar (you can't use them like that in sql expression). Hibernate oracle language does most of converting job (take care there 2 hibernate languages, the one to go was oracle9Dialect) when you chose the hibernate type 'text' instead of String. - Then, there is no initial database for oracle. At the time i did all my tests and patchups, i didn't know either there was a sample database for mysql. Because i was lacking more development time, it has been less time expensive for to drop our oracle patch ups everywhere and to switch to a mysql environment, thought we mainly prefer to concentrate as much as possible oracle here :) Hope you find this information helpful Ludovic Dubost a écrit :