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MODX Community Forums Archive

xPDO Compound Primary Keys

    • 46556
    • 4 Posts
    florian_1990 Reply #1, 12 years, 2 months ago
    I want to make a table with a compound primary key (a primary key consisting of two or more columns). In an older version of xPDO one could just add index="pk" to those fields. How is it done today? I could not find any documentation on that topic.

    Is the following correct?

    <object class="Class" table="table">
    <field key="primary1" dbtype="int" precision="8" phptype="integer" null="false" />
    <field key="primary1" dbtype="int" precision="8" phptype="integer" null="false" />
    <field key="data" dbtype="int" precision="8" phptype="integer" null="false" />

    <index alias="primary" name="primary" primary="true" type="BTREE">
        <column key="primary1" />
        <column key="primary2" />
    </index>
</object>


    (By the way: What does type="BTREE" mean?)
      • 3749
      • 24,544 Posts
      BobRay Reply #2, 12 years, 2 months ago
      There are some advantages to making your object xPDO-friendly by extending xPDOSimpleObject. That automatically gives you a primary autoincrement key of 'id'.

      Then your compound index can be a separate index, like this one from modResource:

      <index alias="content_ft_idx" name="content_ft_idx" primary="false" unique="false" type="FULLTEXT">
            <column key="pagetitle" length="" collation="A" null="false" />
            <column key="longtitle" length="" collation="A" null="false" />
            <column key="description" length="" collation="A" null="false" />
            <column key="introtext" length="" collation="A" null="true" />
            <column key="content" length="" collation="A" null="true" />
        </index>


      If you do want to have a compound primary index, here's how it's done in the MODX schema:

      <index alias="PRIMARY" name="PRIMARY" primary="true" unique="true" type="BTREE">
            <column key="ancestor" length="" collation="A" null="false" />
            <column key="descendant" length="" collation="A" null="false" />
        </index>
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        • 46556
        • 4 Posts
        florian_1990 Reply #3, 12 years, 2 months ago
        Thank you for your reply. I think that solves my problem.