autoincrement

[Rusty Wright]

How do I specify an autoincrement column such that the generated sql 
works with both mysql and postgresql?  In my database xml file I have

<?xml version="1.0"?>
<!DOCTYPE database SYSTEM "http://db.apache.org/torque/dtd/database.dtd";>
<database name="waitlist" defaultIdMethod="native">
    <table name="waitlist">
        <column name="waitlist_key"
                type="bigint"
                size="20"
                required="true"
                primaryKey="true"
                autoIncrement="true"
        />

When I run this under ant with PostgreSQL it connects to the database 
and gets the following error.  I think it's not creating the sequence 
first.  When I use MySql it does everything without any errors.

ddlToDatabase] WARNING: SQL Command CREATE TABLE waitlist
[ddlToDatabase] (
[ddlToDatabase]     waitlist_key BIGINT NOT NULL UNIQUE DEFAULT 
nextval('waitlist_waitlist_key_seq'),
[ddlToDatabase]     facility VARCHAR(20) NOT NULL,
[ddlToDatabase]     uid VARCHAR(16) NOT NULL,
[ddlToDatabase]     cn VARCHAR(40) NOT NULL,
[ddlToDatabase]     type VARCHAR(20) NOT NULL,
[ddlToDatabase]     platform VARCHAR(8) NOT NULL,
[ddlToDatabase]     signin_time TIMESTAMP NOT NULL,
[ddlToDatabase]     PRIMARY KEY (waitlist_key)
[ddlToDatabase] ) failed with: ERROR: relation "waitlist_waitlist_key_seq" does 
not exist

Thanks