Troubleshooting - Spark

The JDBC driver class must be visible to the primordial class loader on the client session and on all executors. This is because Java's DriverManager class does a security check that results in it ignoring all drivers not visible to the primordial class loader when one goes to open a connection. One convenient way to do this is to modify compute_classpath.sh on all worker nodes to include your driver JARs.
Some databases, such as H2, convert all names to upper case. You'll need to use upper case to refer to those names in Spark SQL.
Users can specify vendor-specific JDBC connection properties in the data source options to do special treatment. For example, spark.read.format("jdbc").option("url", oracleJdbcUrl).option("oracle.jdbc.mapDateToTimestamp", "false"). oracle.jdbc.mapDateToTimestamp defaults to true, users often need to disable this flag to avoid Oracle date being resolved as timestamp.