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[SPARK-10648] [SQL] [BRANCH-1.4] Oracle dialect to handle nonspecific numeric types #9498

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[SPARK-10648] [SQL] [BRANCH-1.4] Oracle dialect to handle nonspecific numeric types #9498

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23 changes: 23 additions & 0 deletions sql/core/src/main/scala/org/apache/spark/sql/jdbc/JdbcDialects.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -125,6 +125,7 @@ object JdbcDialects {

registerDialect(MySQLDialect)
registerDialect(PostgresDialect)
registerDialect(OracleDialect)

/**
* Fetch the JdbcDialect class corresponding to a given database url.
Expand Down Expand Up @@ -222,3 +223,25 @@ 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
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
}
}
}