Pre query execution hook for custom datasources

[Shubham Chaurasia <sh...@gmail.com>]

Hi,

In our custom datasource implementation, we want to inject some query level
information.

For example -

scala> val df = spark.sql("some query")   // uses custom datasource under
the hood through Session Extensions.

scala> df.count //  here we want some kind of pre execution hook just
before the query starts it's execution

Is there a hook or some kind of callback that we can implement to achieve
this?

Or similar to org.apache.spark.sql.util.QueryExecutionListener which
provides callbacks for onSuccess and onFailure when query finishes, we want
something like "*beforeStart()*".

Any ideas on how to implement this?

Thanks,
Shubham