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https://issues.apache.org/jira/browse/SPARK-22706?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Sean Owen updated SPARK-22706:
------------------------------
Priority: Minor (was: Major)
On its surface, it looks like it's because the driver's CLOB implementation
class doesn't implement toString(), or that its ResultSet.getString doesn't do
what you want for a CLOB. That is I think this is a Teradata driver issue, but
can't say I'm 100% sure.
> Cannot read Teradata CLOB column type correctly in Spark 2.2.0
> --------------------------------------------------------------
>
> Key: SPARK-22706
> URL: https://issues.apache.org/jira/browse/SPARK-22706
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.2.0
> Environment: Spark 2.2.0
> Teradata driver version: 16.20.00.02 (terajdbc4.jar)
> I am testing with Mac
> Reporter: Nannan Yu
> Priority: Minor
>
> When I try to read the table from Teradata dababase with URL like
> "jdbc:teradata://IP/Database".
> It works well for most of the column datatype.
> But for the CLOB datatype, it cannot read the correct contest:
> If I am using Spark: it will get some result like this:
> -----------------------------------------------------------------------
> DT_INT | DT_CLOB
>
> ------------------------------------------------------------------------------
> 1 | com.teradata.jdbc.jdk6_SQL_Clob@3cc9ee67
> 2 | com.teradata.jdbc.jdk6_SQL_Clob@7cf9ecad
>
> --------------------------------------------------------------------------------
> Actually, it should show the real Character Large Object as this:
> -----------------------------------------------------------------------
> DT_INT | DT_CLOB
>
> ------------------------------------------------------------------------------
> 1 | JESSIE
> 2 | CATHY
>
> --------------------------------------------------------------------------------
> Note: This issue is not for all the 'CLOB' column datatype, for example,
> DB2-CLOB datatype works fine with Spark.
> For teradata, we have this issue maybe related to this reason:
> https://www.dwhpro.com/teradata-clob/
> " The data of a CLOB column is stored {color:#f6c342}as a separate
> sub-table{color}. " for TeraData CLOB?
> From the Spark SourceCode in the file:
> org/apache/spark/sql/execution/datasources/jdbc/JdbcUtils.scala
> * case StringType* =>
> (rs: ResultSet, row: InternalRow, pos: Int) =>
> // TODO(davies): use getBytes for better performance, if the encoding
> is UTF-8
> row.update(pos, UTF8String.fromString(rs.getString(pos + 1)))
> It seems we cannot use this way for the CLOB column from Teradata.
> Actually, I tried to use some other way to read the CLOB data from Teradata,
> it works well. Also it also works for the DB2-CLOB data.
> case StringType =>
> (rs: ResultSet, row: InternalRow, pos: Int) => {
> val sqlType = rs.getMetaData.getColumnType(pos + 1)
> if (java.sql.Types.CLOB == sqlType) {
> val clobData = rs.getClob(pos + 1);
> if (clobData != null)
> row.update(pos, UTF8String.fromString(clobData.getSubString(1,
> clobData.length().toInt)))
> else
> row.update(pos, UTF8String.fromString(rs.getString(pos + 1)))
> }
> else {
> // TODO(davies): use getBytes for better performance, if the
> encoding is UTF-8
> row.update(pos, UTF8String.fromString(rs.getString(pos + 1)))
> }
> }
> Should we handle the CLOB datatype differently with the normal 'StringType'?
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