Re: Elementary Question

From: Michael Gentry (mgentr..asslight.net)
Date: Tue Apr 20 2010 - 11:17:51 EDT

  • Next message: Joe Baldwin: "Re: Elementary Question"

    Hi Joe,

    The AUTO_PK_SUPPORT table is only used when PK Generation Strategy =
    Default. Cayenne Modeler creates the AUTO_PK_SUPPORT if when
    generating the SQL you check the "Create Primary Key Support"
    checkbox. You don't need AUTO_PK_SUPPORT unless you are using the
    Default strategy on some of your tables.

    Your create statement should look more like:

    CREATE TABLE pickers.product (..., oid BIGINT NOT NULL AUTO_INCREMENT,
    ..., PRIMARY KEY (oid)) ENGINE=InnoDB;

    Make sure your create statement includes the AUTO_INCREMENT option for
    your oid. If you don't have AUTO_INCREMENT as an option, MySQL will
    not auto-increment or generate your PKs.

    mrg

    On Tue, Apr 20, 2010 at 10:15 AM, Joe Baldwin <jfbaldwi..arthlink.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 <jfbaldwi..arthlink.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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