[SPARK-12941][SQL][MASTER] Spark-SQL JDBC Oracle dialect fails to map string datatypes to Oracle VARCHAR datatype

docker-integration-tests/pom.xml

@@ -131,6 +131,19 @@
       <artifactId>postgresql</artifactId>
       <scope>test</scope>
     </dependency>
+    <!-- Oracle ojdbc jar, used for oracle  integration suite for docker testing.
+     See https://github.com/apache/spark/pull/11306 for background on why we need
+     to use a an ojdbc jar for the testcase. The maven dependency here is commented
+     because currently the maven repository does not contain the ojdbc jar mentioned.
+     Once the jar is available in maven, this could be uncommented. -->
+    <!--
+      <dependency>
+        <groupId>com.oracle</groupId>
+        <artifactId>ojdbc6</artifactId>
+        <version>11.2.0.2.0</version>
+        <scope>test</scope>
+      </dependency>
+    -->
     <!-- Jersey dependencies, used to override version.
      See https://github.com/apache/spark/pull/9503#issuecomment-154369560 for
      background on why we need to use a newer Jersey only in this test module;

docker-integration-tests/src/test/scala/org/apache/spark/sql/jdbc/OracleIntegrationSuite.scala

@@ -0,0 +1,80 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.jdbc
+
+import java.math.BigDecimal
+import java.sql.{Connection, Date, Timestamp}
+import java.util.Properties
+
+import org.apache.spark.sql.test.SharedSQLContext
+import org.apache.spark.sql.types._
+import org.apache.spark.tags.DockerTest
+
+/**
+ * This patch was tested using the Oracle docker. Created this integration suite for the same.
+ * The ojdbc6-11.2.0.2.0.jar was to be downloaded from the maven repository. Since there was
+ * no jdbc jar available in the maven repository, the jar was downloaded from oracle site
+ * manually and installed in the local; thus tested. So, for SparkQA test case run, the
+ * ojdbc jar might be manually placed in the local maven repository(com/oracle/ojdbc6/11.2.0.2.0)
+ * while Spark QA test run.
+ *
+ * The following would be the steps to test this
+ * 1. Pull oracle 11g image - docker pull wnameless/oracle-xe-11g
+ * 2. Start docker - sudo service docker start
+ * 3. Download oracle 11g driver jar and put it in maven local repo:
+ *    (com/oracle/ojdbc6/11.2.0.2.0/ojdbc6-11.2.0.2.0.jar)
+ * 4. The timeout and interval parameter to be increased from 60,1 to a high value for oracle test
+ *    in DockerJDBCIntegrationSuite.scala (Locally tested with 200,200 and executed successfully).
+ * 5. Run spark test - ./build/sbt "test-only org.apache.spark.sql.jdbc.OracleIntegrationSuite"
+ *
+ * All tests in this suite are ignored because of the dependency with the oracle jar from maven
+ * repository.
+ */
+@DockerTest
+class OracleIntegrationSuite extends DockerJDBCIntegrationSuite with SharedSQLContext {
+  import testImplicits._
+
+  override val db = new DatabaseOnDocker {
+    override val imageName = "wnameless/oracle-xe-11g:latest"
+    override val env = Map(
+      "ORACLE_ROOT_PASSWORD" -> "oracle"
+    )
+    override val jdbcPort: Int = 1521
+    override def getJdbcUrl(ip: String, port: Int): String =
+      s"jdbc:oracle:thin:system/oracle@//$ip:$port/xe"
+  }
+
+  override def dataPreparation(conn: Connection): Unit = {
+  }
+
+  ignore("SPARK-12941: String datatypes to be mapped to Varchar in Oracle") {
+    // create a sample dataframe with string type
+    val df1 = sparkContext.parallelize(Seq(("foo"))).toDF("x")
+    // write the dataframe to the oracle table tbl
+    df1.write.jdbc(jdbcUrl, "tbl2", new Properties)
+    // read the table from the oracle
+    val dfRead = sqlContext.read.jdbc(jdbcUrl, "tbl2", new Properties)
+    // get the rows
+    val rows = dfRead.collect()
+    // verify the data type is inserted
+    val types = rows(0).toSeq.map(x => x.getClass.toString)
+    assert(types(0).equals("class java.lang.String"))
+    // verify the value is the inserted correct or not
+    assert(rows(0).getString(0).equals("foo"))
+  }
+}

sql/core/src/main/scala/org/apache/spark/sql/jdbc/OracleDialect.scala

@@ -42,4 +42,9 @@ private case object OracleDialect extends JdbcDialect {
       None
     }
   }
+
+  override def getJDBCType(dt: DataType): Option[JdbcType] = dt match {
+    case StringType => Some(JdbcType("VARCHAR2(255)", java.sql.Types.VARCHAR))
+    case _ => None
+  }
 }