Re: [JDBC] Binary Large Objects (LOB/BLOB) in Hibernate and JDBC: Unresolved issues

From: Stefan Keller <sfkeller(at)gmail(dot)com>
To: Oliver Jowett <oliver(at)opencloud(dot)com>
Cc: Radosław Smogura <rsmogura(at)softperience(dot)eu>, Alban Hertroys <haramrae(at)gmail(dot)com>, pgsql-general List <pgsql-general(at)postgresql(dot)org>, pgsql-jdbc(at)postgresql(dot)org
Subject: Re: [JDBC] Binary Large Objects (LOB/BLOB) in Hibernate and JDBC: Unresolved issues
Date: 2012-01-10 06:26:14
Message-ID: CAFcOn29fr2Ep5V5JtT1ObajHDPf436Dd_Gkd-HUtmaRiLxLUqw@mail.gmail.com
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I'm still fumbling in the dark but I think I have a smell:

Does somebody know what supportsLobValueChangePropogation according to
the current JDBC specs?

There's an interesting note there:
> NOTE : I do not know the correct answer currently for databases which (1) are not part of the cruise control process or (2) do not supportsExpectedLobUsagePattern().
http://srcrr.org/java/hibernate/3.6.2/reference/org/hibernate/dialect/PostgreSQLDialect.html#supportsLobValueChangePropogation()

It's currently set to false:
https://github.com/hibernate/hibernate-core/blob/master/hibernate-core/src/main/java/org/hibernate/dialect/PostgreSQLDialect.java

Yours, Stefan

2012/1/9 Oliver Jowett <oliver(at)opencloud(dot)com>:
> On 10 January 2012 06:57, Radosław Smogura <rsmogura(at)softperience(dot)eu> wrote:
>
>> In real world BLOBs are transfered as references, and those references are
>> managed in way as the trigger does. Nacked PG doesn't support deletion, Oid is
>> universal type so it can't be used by GC approach, unles collector will know
>> which Oid is LOB oid.
>
> So you just end up with a conservative collector, not an exact
> collector. In practice conservative collectors work OK. (You can use a
> subtype to identify OIDs-that-refer-to-a-LO as suggested elsewhere in
> the thread if you want an exact collector)
>
> Oliver

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