Re: mapping collections of PC Object types

[Craig Russell <Cr...@Sun.COM>]

Hi Michelle,

On Aug 1, 2005, at 3:32 PM, Michelle Caisse wrote:

> Hi Craig,
>
> Could you take a look at my proposed mapppings and schema below?  I  
> have a few specific questions at the relevant places below.

0. Use a join table, and use foreign keys for the elements to refer  
to the primary table
1. Use a join table, and embed the elements column by column
2. Use a join table, and serialize the elements
3. Serialize the entire ArrayList.

>
> Currently we have, taking ArrayListCollections as an example:
>  public static final String [] fieldSpecs = {
>  "public ArrayList ArrayListOfObject0",
>  "embedded-element=true public ArrayList ArrayListOfObject1",
>  "embedded-element=false public ArrayList ArrayListOfObject2",
> ...
> }
>
> We want:
>  public static final String [] fieldSpecs = {
>  "public ArrayList ArrayListOfObject0",   [ArrayList in join table,  
> elements in join tables]
>  "embedded-element=true public ArrayList ArrayListOfObject1",    
> [ArrayList in join table, elements embedded]
>  "embedded-element=false <element serialized=true> public ArrayList  
> ArrayListOfObject2",   [ArrayList in join table, elements serialized]
>  "serialized=true public ArrayList ArrayListOfObject3",  [ArrayList  
> serialized in columns of primary table]
>
> ** QUESTION: I'm not sure how much to attempt to test defaults  
> (unspecified values for embedded-element, serialized.

You have the default case in ArrayListOfObject0. It defaults to  
serialized=false, embedded-element=false, using a join table.

What you don't have is the explicit serialized=false, embedded- 
element=false. I don't know that it's important.

> ______
> orm:
>
> <orm>
>    <package name="org.apache.jdo.tck.pc.fieldtypes">
>        <class name="ArrayListCollections"  
> table="ARRAYLIST_COLLECTIONS">
>            <field name="identifier" column="IDENTIFIER" primary- 
> key="true"/>
>            <field name="ArrayListOfObject0"
>                   table="ARRAYLIST_OF_OBJECT0">
>                <join column="IDENTIFIER"/>
>                <element column="OBJREF">
>                     <foreign-key/>
>                </element>
>                <order column="INDEX"/>
>            </field>
>            <field name="ArrayListOfObject1"
>                   table="ARRAYLIST_OF_OBJECT1">
>                 <element>
>                     <embedded>
>                       <field="intval" column="INTVAL"/>
>                       <field="stringval" column="STRINGVAL"/>
>                    </embedded>
>                 </element>
>               <order column="INDEX"/>
>            </field>
>            <field name="ArrayListOfObject2"
>                   table="ARRAYLIST_OF_OBJECT2">
>                <join column="IDENTIFIER"/>
>                <element column="OBJVAL" serialized="true"/>
>                <order column="INDEX"/>
>            </field>
>             <!-- QUESTION: Is it necessary to specify  
> serialized="true" for this field? -->

Yes, because serialized=true is not (ever) the default for a field.

>            <field name="ArrayListOfObject3"
>                   column="ARRAYLIST_OF_OBJECT3" serialized="true">
>            </field>
> ...
> ______
> jdo:
>
> <jdo>
> <package name="org.apache.jdo.tck.pc.fieldtypes">
> <class name="ArrayListCollections" identity-type="application"
>    objectid- 
> class="org.apache.jdo.tck.pc.fieldtypes.ArrayListCollections$Oid">
> <field name="identifier" primary-key="true"/>
> <field name="ArrayListOfObject0" >
> <collection element-type="java.lang.Object">
> </collection>
> </field>
> <field name="ArrayListOfObject1" >
> <collection element-type="java.lang.Object" embedded-element="true">
> </collection>
> </field>
> <field name="ArrayListOfObject2" >
> <!-- QUESTION: Is embedded-element true, false, or n/a?? -->

It's n/a. The mapping is embedded serialized so this doesn't matter.

Craig


> <collection element-type="java.lang.Object" embedded-element="false">
> </collection>
> </field>
> <field name="ArrayListOfObject3" >
> <collection element-type="java.lang.Object">
> </collection>
> </field>
> ...
> ______
> Schema:
>
> CREATE TABLE ARRAYLIST_COLLECTIONS
> (
>    IDENTIFIER INTEGER NOT NULL,
>    ARRAYLIST_OF_OBJECT3 LONG VARCHAR FOR BIT DATA,
>    ARRAYLIST_OF_SIMPLE_CLASS3 LONG VARCHAR FOR BIT DATA,
>    ARRAYLIST_OF_SIMPLE_INTERFACE3 LONG VARCHAR FOR BIT DATA,
>    ...
> );
>
> -- element neither serialized nor embedded
> CREATE TABLE ARRAYLIST_OF_OBJECT-
> (
>    IDENTIFIER INTEGER REFERENCES ARRAYLIST_COLLECTIONS NOT NULL,
>    OBJREF BIGINT REFERENCES SIMPLE_CLASS NOT NULL,
>    INDEX INTEGER NOT NULL
> );
>
> -- embedded-element="true"
> CREATE TABLE ARRAYLIST_OF_OBJECT1
> (
>    IDENTIFIER INTEGER REFERENCES ARRAYLIST_COLLECTIONS NOT NULL,
>    INTVAL INTEGER NOT NULL,
>    STRINGVAL VARCHAR(128) NOT NULL,
>    INDEX INTEGER NOT NULL
> );
>
> -- <element serialized="true">
> CREATE TABLE ARRAYLIST_OF_OBJECT2
> (
>    IDENTIFIER INTEGER REFERENCES ARRAYLIST_COLLECTIONS NOT NULL,
>    OBJVAL LONG VARCHAR FOR BIT DATA,
>    INDEX INTEGER NOT NULL
> );
>
> Thanks!
>
> -- Michelle
>

Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:Craig.Russell@sun.com
P.S. A good JDO? O, Gasp!