I found the examples for JDBC connection are mostly read the whole table and then do operations like joining.
val jdbcDF = sqlContext.read.format("jdbc").options(
Map("url" -> "jdbc:postgresql:dbserver",
"dbtable" -> "schema.tablename")).load()
Sometimes it is not practical since the whole table data is too big and not necessary.
What makes sense to me is to use sparksql to get subset data from oracle tables using sql-like statement.
I couldn't find such examples. Can someone show me?