[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-468) MysqlDialect incorrectly maps java.lang.Boolean to SQL BIT

[Nikita D (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=38866#action_38866 ] 

Nikita D commented on HHH-468:
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Perhaps the root problem is in org.hibernate.type.BooleanType, whose sqlType() method returns java.sql.Types.BIT. Because of this, for a field whose type is a java boolean/Boolean, the dialect class is actually asked to map a java.sql.Types.BIT to its String column type. The MySQL dialect returns "bit" as the String for java.sql.Types.BIT, but I think this actually makes sense since MySQL supports both BIT and BOOLEAN (see http://dev.mysql.com/doc/refman/5.0/en/numeric-type-overview.html). java.sql.Types also defines both BIT and BOOLEAN.

>From what I understand, here is how the mapping happens right now:
 * The MySQL dialect registers the column type mapping registerColumnType( Types.BIT, "bit" ). It doesn't register anything for java.sql.Types.BOOLEAN.
 * When generating the DDL, SchemaExport calls Configuration.generateSchemaCreationScript(). For each column, the SQL type is retrieved using Column.getSqlType().
 * Column.getSqlType() gets the java.sql.Types type from the org.hibernate.type.Type of the Column. This is where the org.hibernate.type.BooleanType returns java.sql.Types.BIT.
 * The dialect's method getTypeName() is invoked with the java.sql.Types type in order to get the string representation for the JDBC SQL type code.

So to me, it seems that the issue is the mapping from the java boolean/Boolean to the java.sql.Types type, not in the dialect's mapping of the java.sql.Types type to its String representation. If the MySQL dialect registered the type java.sql.Types.BOOLEAN, and if org.hibernate.type.BooleanType returned java.sql.Types.BOOLEAN, booleans would be mapped correctly. The problem is, I am not sure what the repercussions are of changing org.hibernate.type.BooleanType.sqlType() or if there are particular reasons for it to be implemented the way it is right now.

> MysqlDialect incorrectly maps java.lang.Boolean to SQL BIT
> ----------------------------------------------------------
>
>                 Key: HHH-468
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-468
>             Project: Hibernate Core
>          Issue Type: Bug
>    Affects Versions: 3.0.3
>         Environment: Hibernate 3.0, MySQL.
>            Reporter: Mark Matthews
>            Assignee: Scott Marlow
>
> I didn't track down how java.lang.Boolean gets mapped to Types.BIT in hibernate, but you probably _don't_ want to map to "bit" like you do in MysqlDialect. 
> "bit", according to SQL99 (it's not in the core standard, and the type was actually dropped for sql2k3) is a bitfield, not a boolean value. You can of course define a bit(1), but it is technically more correct for java.lang.Boolean to map to a SQL BOOLEAN for MySQL since we support a BOOLEAN and a BIT. 
> It looks like the JDBC-3.0 guys ignored what the standard said, because in reality you'd want BIT to map to something like byte[], or java.util.BitSet if you were tracking how the SQL standard defines BIT.
> I'm guessing you probably want to map to "boolean", which the JDBC driver will automagically convert for you, as it silently maps to TINYINT(1) on the server side.

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