Why has Hibernate switched to use LONG over CLOB?

StackOverflow https://stackoverflow.com/questions/3719905

Question

It looks like that Hibernate started using LONG data type in version 3.5.5 (we upgraded from 3.2.7) instead of CLOB for the property of type="text".

This is causing problems as LONG data type in Oracle is an old outdated data type (see http://www.orafaq.com/wiki/LONG) that shouldn’t be used, and tables can’t have more than one column having LONG as a data type.

Does anyone know why this has been changed?

I have tried to set the Oracle SetBigStringTryClob property to true (as suggested in Hibernate > CLOB > Oracle :(), but that does not affect the data type mapping but only data transfer internals which are irrelevant to my case.

One possible fix for this is to override the org.hibernate.dialect.Oracle9iDialect: 

public class Oracle9iDialectFix extends Oracle9iDialect {
  public Oracle9iDialectFix() {
    super();
    registerColumnType(Types.LONGVARCHAR, "clob");
    registerColumnType(Types.LONGNVARCHAR, "clob");
  }
}

However this is the last resort - overriding this class is step closer to forking Hibernate which I would rather avoid doing.

Can anybody explain why this was done? Should this be raised as a bug?

[UPDATE]: I have created https://hibernate.atlassian.net/browse/HHH-5569, let's see what happens.

Was it helpful?

Solution

It looks like the resolution to this issue is to use materialized_clob, at least that's what's being said by Gail Badner on HHH-5569.

This doesn't help me at all (and I left relevant comment about that) but might be helpful for someone else here. Anyway the bug is rejected and there is very little I can do about it but use overriden dialect :(

OTHER TIPS

Can anybody explain why this was done? Should this be raised as a bug?

This has been done for HHH-3892 - Improve support for mapping SQL LONGVARCHAR and CLOB to Java String, SQL LONGVARBINARY and BLOB to Java byte[] (update of the documentation is tracked by HHH-4878).

And according to the same issue, the old behavior was wrong.

(NOTE: currently, org.hibernate.type.TextType incorrectly maps "text" to java.sql.Types.CLOB; this will be fixed by this issue and updated in database dialects)

You can always raise an issue but in short, my understanding is that you should use type="clob" if you want to get the property mapped to a CLOB.

PS: Providing your own Dialect and declaring it in your Hibernate configuration (which has nothing to do with a fork) is IMHO not a solution on the long term.

I cannot answer your question about why, but for Hibernate 6, it seems they're considering switching back to using CLOB

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