WSO2 DAS SiddhiQL：动态事件表/持久事件流

Question

I would like to know if WSO2 Data Analytics Server allows to define a dynamic events tables or dynamic streams. For example, imagine one event represent a car, and in this event, an attribute is the 'brand' of the car (Ford, Mercedes, Audi ...).

And I would like to add a column each time there is a new different brand. So my table would look like this :

And thus, if I receive an event with the brand 'Toyota', it would add a column to my table which would look like this:

Considering that I don't know in advance the number of different brands I will receive, I need this to be dynamic.

Answer 1

Dynamically changing the schema of an event table is not possible. This is because the schema of the event table is defined when the Siddhi execution plan is deployed. Once it is deployed, the schema cannot be changed.

On the other hand, it looks like what you need here is not an event table.

Perhaps, what you need to do is to update the schema of a table (an RDBMS table) when a certain event happens (for example, when a car event arrives with a new brand). Do you use this updated table in your Siddhi execution plan? If you do not use it, then you do not need an event table. Please correct me if I have misunderstood your requirement.

If your requirement is to update the schema of a table when a certain event happens, then you might need to write a custom event publisher to do that. If so, please refer the document on the same: Building Custom Event Publishers .