According to the current design of the JDBC adapter, it is not possible to reuse the vector schema roots. That is, a new vector schema root is created and released for each batch.
This can cause performance problems, because in many scenarios, the client code only reads data in vector schema root. So the vector schema roots can be reused in the following cycle: populate data -> client use data -> populate data -> ...
The current design has another problem. For most times, it has two alternating vector schema roots in memory, causing a large waste of memory, especially for large batches.
We solve both problems by providing a flag in the config, which allows the user to reuse the vector shema roots.