Auto-Increment Precondition

Some of my databases have an auto-increment on the id column of my log table, while others don't. As I need this auto-increment on all of my databases, I created a changeSet like this:

1.     <changeSet id="1" author="emi">
2.         <addAutoIncrement columnDataType="int"
3.                 columnName="id"
4.                 incrementBy="1"
5.                 startWith="1"
6.                 tableName="log"/>
7.     </changeSet>

However, this fails when I run it on my databases that already have this auto-increment.

I'd like something like this:

1.     <changeSet id="1" author="emi">
2.         <preConditions>
3.                   <not>
4.                         <autoIncrementExists columnName="id"
5.                               tableName="log"/>
6.                   </not>
7.         </preConditions>
8.         <addAutoIncrement columnDataType="int"
9.                 columnName="id"
10.                 incrementBy="1"
11.                 startWith="1"
12.                 tableName="log"/>
13.     </changeSet>

Is this possible in any way?

PS: If you're wondering why I ended up with this inconsistency on my databases, it's because MySQL deletes the auto-increment when you change a column type, while PostgreSQL doesn't.