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limit number of joins for use with mysql?

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srhib

Post subject: limit number of joins for use with mysql?

Posted: Thu Sep 04, 2003 3:40 am

Newbie

Joined: Thu Sep 04, 2003 3:36 am
Posts: 11
Location: Karlsruhe/Germany

hi,

is there a way to limit the number of tables used in hibernate-generated joins?
we are using hibernate 2 with mysql 4.1a and it sometimes says
"Too many tables. MySQL can only use 31 tables in a join"

kind regards
philipp

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gavin

Post subject:

Posted: Thu Sep 04, 2003 3:45 am

Hibernate Team

Joined: Tue Aug 26, 2003 12:50 pm
Posts: 5130
Location: Melbourne, Australia

Hibernate 2.1 has a new config property called:

hibernate.max_fetch_depth

which can be used to limit how deep outerjoin fetching goes by default.

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srhib

Post subject:

Posted: Thu Sep 04, 2003 5:00 am

Newbie

Joined: Thu Sep 04, 2003 3:36 am
Posts: 11
Location: Karlsruhe/Germany

thanks gavin,
i've tried version 2.1 but now our subclass-mappings don't work anymore.
hibernate says
'Repeated column in mapping for class <fill in subclass-name here> should be mapped with insert="false" update="false"' while initializing and i can't find any information on that.

philipp

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gavin

Post subject:

Posted: Thu Sep 04, 2003 5:14 am

Hibernate Team

Joined: Tue Aug 26, 2003 12:50 pm
Posts: 5130
Location: Melbourne, Australia

Do as it says! Use insert="false" update="false" to prevent repeated columns in an SQL INSERT/UPDATE.

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srhib

Post subject:

Posted: Thu Sep 04, 2003 8:02 am

Newbie

Joined: Thu Sep 04, 2003 3:36 am
Posts: 11
Location: Karlsruhe/Germany

Perhaps i have to change the subject to "stupid subclass question" now but i didn't get it yet.
We use XDoclet to generate the mapping documents. It worked fine with version 2.0.1 but version 2.1 doesn't accept the subclass-mappings:

Code:

<hibernate-mapping>
    <class
        name="ClassA"
        table="TEXT"
        dynamic-update="false"
        dynamic-insert="false"
        discriminator-value="DISC_A"
    >

        <id
           ...
        </id>

        <discriminator
            column="TYPE"
            type="string"
            length="30"
        />

        <property
            name="propX"
            type="string"
            column="PROP_X"
            length="2"
        />

        <property
            name="propY"
            type="string"
            column="PROP_Y"
            length="3"
        />

        <property
         ...
        />

        <subclass
            name="ClassB"
            dynamic-update="false"
            dynamic-insert="false"
            discriminator-value="DISC_B"
        >

        </subclass>
        <subclass
            name="ClassC"
            dynamic-update="false"
            dynamic-insert="false"
            discriminator-value="DISC_C"
        >

        ...

So please give me a hint what to change in the mapping documents.

Thanks
Philipp

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gavin

Post subject:

Posted: Thu Sep 04, 2003 8:07 am

Hibernate Team

Joined: Tue Aug 26, 2003 12:50 pm
Posts: 5130
Location: Melbourne, Australia

Not on the <subclass> elements!

On the <property> with the repeated column mapping!

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