Can't fetch clob and long in one select/query

Question

I created a nightmare table containing numerous binary data types to test an application I was working on, and believe I have found an undocumented bug in Oracle's JDBC drivers that is preventing me from loading a CLOB and a LONG in a single SQL select statement. I can load the CLOB successfully, but attempting to call ResultSet.get...() for the LONG column always results in
java.sql.SQLException: Stream has already been closed
even when processing the columns in the order of the SELECT statement.
I have demonstrated this behaviour with version 9.2.0.3 of Oracle's JDBC drivers, running against Oracle 9.2.0.2.0.
The following Java example contains SQL code to create and populate a table containing a collection of nasty binary columns, and then Java code that demonstrates the problem.
I would really appreciate any workarounds that allow me to pull this data out of a single query.
import java.sql.*;
This class was developed to verify that you can't have a CLOB and a LONG column in the
same SQL select statement, and extract both values. Calling get...() for the LONG column
always causes 'java.sql.SQLException: Stream has already been closed'.
CREATE TABLE BINARY_COLS_TEST
PK INTEGER PRIMARY KEY NOT NULL,
CLOB_COL CLOB,
BLOB_COL BLOB,
RAW_COL RAW(100),
LONG_COL LONG
INSERT INTO BINARY_COLS_TEST (
PK,
CLOB_COL,
BLOB_COL,
RAW_COL,
LONG_COL
) VALUES (
1,
'-- clob value --',
HEXTORAW('01020304050607'),
HEXTORAW('01020304050607'),
'-- long value --'
public class JdbcLongTest
public static void main(String argv[])
throws Exception
Driver driver = (Driver)Class.forName("oracle.jdbc.driver.OracleDriver").newInstance();
DriverManager.registerDriver(driver);
Connection connection = DriverManager.getConnection(argv[0], argv[1], argv[2]);
Statement stmt = connection.createStatement();
ResultSet results = null;
try
String query = "SELECT pk, clob_col, blob_col, raw_col, long_col FROM binary_cols_test";
results = stmt.executeQuery(query);
while (results.next())
int pk = results.getInt(1);
System.out.println("Loaded int");
Clob clob = results.getClob(2);
// It doesn't work if you just close the ascii stream.
// clob.getAsciiStream().close();
String clobString = clob.getSubString(1, (int)clob.length());
System.out.println("Loaded CLOB");
// Streaming not strictly necessary for short values.
// Blob blob = results.getBlob(3);
byte blobData[] = results.getBytes(3);
System.out.println("Loaded BLOB");
byte rawData[] = results.getBytes(4);
System.out.println("Loaded RAW");
byte longData[] = results.getBytes(5);
System.out.println("Loaded LONG");
catch (SQLException e)
e.printStackTrace();
results.close();
stmt.close();
connection.close();
} // public class JdbcLongTest

Answer 1

The problem is that LONGs are not buffered but are read from the wire in the order defined. The problem is the same as
rs = stmt.executeQuery("select myLong, myNumber from tab");
while (rs.next()) {
int n = rs.getInt(2);
String s = rs.getString(1);
The above will fail for the same reason. When the statement is executed the LONG is not read immediately. It is buffered in the server waiting to be read. When getInt is called the driver reads the bytes of the LONG and throws them away so that it can get to the NUMBER and read it. Then when getString is called the LONG value is gone so you get an exception.
Similar problem here. When the query is executed the CLOB and BLOB locators are read from the wire, but the LONG is buffered in the server waiting to be read. When Clob.getString is called, it has to talk to the server to get the value of the CLOB, so it reads the LONG bytes from the wire and throws them away. That clears the connection so that it can ask the server for the CLOB bytes. When the code reads the LONG value, those bytes are gone so you get an exception.
This is a long standing restriction on using LONG and LONG RAW values and is a result of the network protocol. It is one of the reasons that Oracle deprecates LONGs and recommends using BLOBs and CLOBs instead.
Douglas