[SPARK-10648][SQL][BRANCH-1.4] Oracle dialect to handle nonspecific n…

…umeric types This backports apache#9495 to branch-1.4 (in case anyone needs this). Author: Yin Huai <[email protected]> Closes apache#9498 from yhuai/OracleDialect-1.4.
leonelfolmer · Nov 5, 2015 · 6c5e9a3 · 6c5e9a3
1 parent 00efa3c
commit 6c5e9a3
Showing 1 changed file with 26 additions and 0 deletions.
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/jdbc/JdbcDialects.scala b/sql/core/src/main/scala/org/apache/spark/sql/jdbc/JdbcDialects.scala
@@ -125,6 +125,7 @@ object JdbcDialects {
 
   registerDialect(MySQLDialect)
   registerDialect(PostgresDialect)
+  registerDialect(OracleDialect)
 
   /**
    * Fetch the JdbcDialect class corresponding to a given database url.
@@ -222,3 +223,28 @@ case object MySQLDialect extends JdbcDialect {
     s"`$colName`"
   }
 }
+
+/**
+ * :: DeveloperApi ::
+ * Default Oracle dialect, mapping a nonspecific numeric type to a general decimal type.
+ */
+@DeveloperApi
+case object OracleDialect extends JdbcDialect {
+  override def canHandle(url: String): Boolean = url.startsWith("jdbc:oracle")
+  override def getCatalystType(
+      sqlType: Int, typeName: String, size: Int, md: MetadataBuilder): Option[DataType] = {
+    // Handle NUMBER fields that have no precision/scale in special way
+    // because JDBC ResultSetMetaData converts this to 0 precision and -127 scale
+    // For more details, please see
+    // https://github.com/apache/spark/pull/8780#issuecomment-145598968
+    // and
+    // https://github.com/apache/spark/pull/8780#issuecomment-144541760
+    if (sqlType == Types.NUMERIC && size == 0) {
+      // This is sub-optimal as we have to pick a precision/scale in advance whereas the data
+      // in Oracle is allowed to have different precision/scale for each value.
+      Some(DecimalType(38, 10))
+    } else {
+      None
+    }
+  }
+}