Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/15664#discussion_r94063172
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/jdbc/JdbcUtils.scala
---
@@ -211,6 +211,55 @@ object JdbcUtils extends Logging {
}
/**
+ * Returns the schema if the table already exists in the JDBC database.
+ */
+ def getSchema(conn: Connection, url: String, table: String):
Option[StructType] = {
+ val dialect = JdbcDialects.get(url)
+
+ try {
+ val statement = conn.prepareStatement(dialect.getSchemaQuery(table))
+ try {
+ Some(getSchema(statement.executeQuery(), dialect))
+ } catch {
+ case _: SQLException => None
+ } finally {
+ statement.close()
+ }
+ } catch {
+ case _: SQLException => None
+ }
+ }
+
+ /**
+ * Returns a schema using rddSchema's column sequence and tableSchema's
column names.
+ *
+ * When appending data into some case-sensitive DBMSs like
PostgreSQL/Oracle, we need to respect
+ * the existing case-sensitive column names instead of RDD column names
for user convenience.
+ * See SPARK-18123 for more details.
+ */
+ def normalizeSchema(
+ rddSchema: StructType,
+ tableSchema: StructType,
+ caseSensitive: Boolean): StructType = {
--- End diff --
`isCaseSensitive`
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