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From Chris Poulsen <mailingl...@nesluop.dk>
Subject Re: Oracle Sequences & Cache
Date Thu, 16 Jun 2011 16:49:30 GMT
Hi Bruno,

We've had issues at work related to caching of sequence values on oracle if
I recall correctly. We're using cayenne 3.

As we're not doing bulk inserts through cayenne, we decided to simply
extract one key at the time (not cache). The following xml snippet shows how
we configure the db-key-generator to do this (IIRC setting the cache-size to
0 fails, even though would I find that the intuitive way to tell cayenne not
to cache the key):

    <db-entity name="PORTABLE_KIT_CONTACT_PERSON"
schema="CPC_PK_MANAGEMENT">
        <db-attribute name="NAME" type="VARCHAR" isMandatory="true"
length="256"/>
        <db-attribute name="PERSON_KEY" type="INTEGER" length="16"/>
        <db-attribute name="P_K_CONTACT_PERSON_KEY" type="INTEGER"
isPrimaryKey="true" isMandatory="true" length="22"/>
        <db-attribute name="TELEPHONE_NUMBER" type="VARCHAR"
isMandatory="true" length="64"/>
        <db-key-generator>
            <db-generator-type>ORACLE</db-generator-type>
            <db-generator-name>PK_CONTACT_PERSON_KEY_SEQ</db-generator-name>
            <db-key-cache-size>1</db-key-cache-size>
        </db-key-generator>
    </db-entity>

Using an insert "returning" a trigger generated key instead of the
key-generator stuff would be a nice (returning is supported since Oracle
10.2 or something like that). But I don't know if it would be a trivial
change to cayenne.

Hope this helps.

-- 
Regards Chris

On Thu, Jun 16, 2011 at 5:36 PM, Bruno René Santos <brunorene@holos.pt>wrote:

> Hello all,
>
> We had a problem on one of our applications on Oracle because, we think, of
> the cayenne cache and we wanted to have some sort of confirmation if we are
> seeing this correctly...
>
> On Oracle, in order to get the next PK we need to execute the query:
>
> Select sequence_name.next_val from DUAL
>
> Sometimes the query logger did not print this command before an INSERT.
> After some testing we reached to the conclusion that this was a cache issue
> and so we overrode CommitChanges and CommitChangesToParent in order to clear
> the query cache after the commit phase, like this:
>
> @Override
>    public void commitChanges() throws CayenneRuntimeException {
>        super.commitChanges();
>        getQueryCache().clear();
>    }
>
>    @Override
>    public void commitChangesToParent() {
>        super.commitChangesToParent();
>        getQueryCache().clear();
>    }
>
> We think this is a bug because on the PK generation phase on cayenne no
> data, always, should be ever retrieved from the cache, which would lead to
> repeated primary keys...
>
> Can this be true?
>
> Thanx
> Bruno
> --
> Bruno René Santos | brunorene@holos.pt <mailto:brunorene@holos.pt> |
> Gestor de Projectos | Analista | Programador | Investigador
>
> Holos - Soluções Avançadas em Tecnologias de Informação S.A.
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> Rua dos Inventores . Quinta da Torre . 2825 - 182 Caparica . Portugal
> Phone: +351 210 438 686 . Fax: +351 210 438 687 . Web: www.holos.pt
>
>
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