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From Robert Zeigler <robert.zeig...@roxanemy.com>
Subject Re: Elementary Question
Date Tue, 20 Apr 2010 20:24:52 GMT
Cayenne generates the appropriat AUTO_PK_SUPPORT table regardless of the pk
generation strategy, but if your pk generation strategy is "Database
Generated" (AND if your db + driver support auto-pk generation), it won't
actually use it; it will allow the database to generate the id and use the
generated id.

Robert

On Tue, Apr 20, 2010 at 9:15 AM, Joe Baldwin <jfbaldwin@earthlink.net>wrote:

> Michael,
>
> I need a simple verification (because the webhost tech person is very
> confused).
>
> To explain further: I am using Cayenne Modeler to design the entities, and
> to create the database tables in MySQL. (i.e. Tools - Generate Database
> Schema).  My understanding, and my tests have proved, if you set [PK
> Generation Strategy] to "Database-Generated", and [Auto Incremented] to "oid
> (INTEGER)" then Cayenne Modeler will "request/instruct/ask " MySQL to create
> a table, then set the oid as the primary key, and set auto_increment to
> "true" for that field.
>
> The following code was generated by the Cayenne Modeler (I deleted
> everything not having to do with the table or key)
>
>        CREATE TABLE pickers.product (PRIMARY KEY (oid)) ENGINE=InnoDB;
>        CREATE TABLE AUTO_PK_SUPPORT (  TABLE_NAME CHAR(100) NOT NULL,
>  NEXT_ID BIGINT NOT NULL, UNIQUE (TABLE_NAME));
>        DELETE FROM AUTO_PK_SUPPORT WHERE TABLE_NAME IN ('product');
>        INSERT INTO AUTO_PK_SUPPORT (TABLE_NAME, NEXT_ID) VALUES ('product',
> 200);
>
>
> The question now is: Has Cayenne Modeler generated SQL that creates a table
> named "product", with a primary key "oid", whose value is automatically
> created by MySQL's InnoDB engine, using auto_increment, at the time of the
> INSERT?  Another way of asking this is: In this scenario, does Cayenne
> generate the key, or does MySQL generate the key?
>
> I would like to forward a brief response to the webhost.
>
> Thanks,
> Joe
>
>
>
>
> On Apr 20, 2010, at 9:25 AM, Michael Gentry wrote:
>
> > Hi Joe,
> >
> > Your wording on #2 and #3 was a little curious to me.  I don't know if
> > you used Cayenne Modeler to generate your schema or if you are using
> > an existing schema.  Cayenne (at runtime) doesn't really instruct the
> > database (MySQL) to auto-generate keys.  Cayenne will nont provide a
> > value for "oid" when inserting the record and that essentially
> > instructs MySQL to auto-generate a key.  You set this up when you
> > create your product table, for example.  The database needs to know
> > that it is responsible for auto-generating the keys -- Cayenne won't
> > tell it at runtime (other than leaving the key out on insert).
> >
> > Maybe I'm a bit off on what you were asking, but it seems like you are
> > expecting Cayenne to tell MySQL to generate the keys when it actually
> > works the other way around: MySQL is supposed to know to generate the
> > key and Cayenne then asks it for the key it generated.
> >
> > mrg
> >
> > PS. BTW, your settings are correct to use the auto-generated key
> > feature in MySQL, just be sure the table was created to auto-generate
> > on your "oid" column.
> >
> >
> > On Mon, Apr 19, 2010 at 8:03 PM, Joe Baldwin <jfbaldwin@earthlink.net>
> wrote:
> >> I apologize for this, but I am being forced to verify a configuration
> that is pretty obvious.
> >>
> >> Please refer to the attached CM configuration panel for an Entity.
> >>
> >> 1. The Primary Key "PK Generation Strategy" is set to
> "Database-Generated".  Please verify that this means that the PK Generation
> Strategy is Database Generated.
> >> 2. The Primary Key "Auto Increment" is set to "oid (INTEGER)".  Please
> verify that the field being auto-incremented is "oid".
> >> 3. Please verify that (with the DBMS set to MySQL) that the two previous
> parameters instruct MySQL to use its auto_increment feature to create a new
> "oid" value for inserted records.
> >>
> >> Thanks
> >> Joe
> >>
> >>
> >>
>
>

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