In a project, I have to propagate several aggregated columns across several tables using the AggregateColumn behavior. It is similar to having items, which are aggregated on their groups, which are aggregated on their owner. This works fine, except I noticed that the AggregateColumn behavior causes extensive update cascades when changing the aggregation source table. In my project, there are four aggregation columns on three tables, and a single insert, update or delete on the source table causes a whooping 32 subsequent updates. This has become a problem, particularly when deleting several items takes about a minute, when it should be a fraction of a second.
Reason for the update cascade is that AggregateColumn behavior triggers a save for each aggregation, which in turn triggers the full aggregation on the parent table, and so on, leading to exponential complexity.

I figured there is an easy solution for this: just have AggregateColumn do all the aggregations and only then trigger save, and we are back at linear complexity. In my project, that means 3 instead of 32 updates, and easy adjustment in case of delete. So that's fantastic, and easy to implement using Propel behavior.
However, I need Propel schema definition to supply a list of columns to the behavior, and this is currently not supported. Even if I wrote my own little behavior, the only way to get it working is with some funky business, like putting json into an xml parameter attribute. Bummer. If only there were parameter list support in the schema parser...

Long story short, I figured I can do it in Propel itself, for the sake of the blazing fast of everybody. Seems to work nicely, all the tests run through. Hope you can use it, so I don't have to monkey patch around the issue.

For reference, the behavior can be declared like this:

<behavior name="aggregate_multiple_columns" id="...">
    <parameter name="foreign_table" value="score"/>
    <parameter-list name="columns">
        <parameter-list-item>
            <parameter name="column_name" value="total_score" />
            <parameter name="expression" value="SUM(score)" />
        </parameter-list-item>
        <parameter-list-item>
            <parameter name="column_name" value="number_of_scores" />
            <parameter name="expression" value="COUNT(score)" />
        </parameter-list-item>
    </parameter-list>
</behavior>

If you have feedback, I am happy to hear it!
Thank you, best wishes