[jira] [Created] (ISIS-812) Isis 1.5 blob mapping broken for PostgreSQL (when set to null)

["Dan Haywood (JIRA)" <ji...@apache.org>]

Dan Haywood created ISIS-812:
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             Summary: Isis 1.5 blob mapping broken for PostgreSQL (when set to null)
                 Key: ISIS-812
                 URL: https://issues.apache.org/jira/browse/ISIS-812
             Project: Isis
          Issue Type: Bug
          Components: Archetype: ToDoApp WRJ, Objectstore: JDO
    Affects Versions: objectstore-jdo-1.5.0, archetype-quickstart-wrj-1.5.0
            Reporter: Dan Haywood
            Assignee: Dan Haywood
            Priority: Minor
             Fix For: archetype-quickstart_wrj-1.6.0, objectstore-jdo-1.6.0


As reported on mailing list: http://markmail.org/thread/zoiu2v4sklo7mevq

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Looking into this, I've learnt that PostgreSQL does not support BLOB datatype, but instead supports "bytea" (byte array) and "oid".  The first is in-row storage, where the data is always returned in the result set, the second is a pointer to off-row storage; PostgreSQL provides its own API for handling oid types).

For the Isis Blob class (org.apache.isis.applib.value.Blob) we provide our own IsisBlobMapping; this is automatically registered through metadata held in the JDO applib jar.   It is the job of this mapping class to read/set values on the underlying ResultSet / PreparedStatement.  DataNucleus provides some additional wrapping infrastructure.

The warning mentioned in the mailing list post indicates that DN is treating the BLOB datatype as a "bytea".  This *almost* works fine; our IsisBlobMapping can persist non-null values ok, but attempting to set a null value breaks PostgreSQL; it treats the null as a null pointer of type "oid" (offline storage), rather than a null of type "bytea".

After some experimentation, I've found a different way to set null that works for PostgreSQL and also works fine for HSQLDB, and MS SQL Server.

This ticket is to apply that change.



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