Github user LucaCanali commented on a diff in the pull request:
https://github.com/apache/spark/pull/18724#discussion_r132679699
--- Diff: sql/core/src/test/scala/org/apache/spark/sql/jdbc/JDBCSuite.scala
---
@@ -1007,4 +1007,23 @@ class JDBCSuite extends SparkFunSuite
assert(sql("select * from people_view").count() == 3)
}
}
+
+ test("SPARK-21519: option sessionInitStatement, run SQL to initialize
the database session.") {
+ val initSQL1 = "SET @MYTESTVAR 21519"
+ val df1 = spark.read.format("jdbc")
+ .option("url", urlWithUserAndPass)
+ .option("dbtable", "(SELECT NVL(@MYTESTVAR, -1))")
+ .option("sessionInitStatement", initSQL1)
+ .load()
+ assert(df1.collect() === Array(Row(21519)))
+
+ val initSQL2 = "SET SCHEMA DUMMY"
--- End diff --
Thanks for the clarification. I have now added a test that runs 2 SQL
statements.
For future reference I'd like to stress the fact that the code executed by
the option "sessionInitStatement" is just the user-provided string fed through
the execute method of the JDBC connection, so it can use the features of the
target database language/syntax. In the case of the test I wrote for the H2
database I have just put together two commands separated by ";". When using
sessionInitStatement for querying Oracle, for example, the user-provided
command can be a SQL statemnet or a PL/SQL block grouping multiple commands and
logic.
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