When you import data (e.g. via JDBC) using external tables and Spark, the staging table feature allows for preprocessing the data, e.g. data cleaning or schema mapping, on Spark side before loading it into Vector. This feature is supported only with Spark Vector Connector 3.0 in conjunction with Spark 3.0

For more information, see Load Data with Spark SQL through the Spark-Vector Connector in the Getting Started Guide.