ODP.NET, Managed reading LONG column results in ORA-01009 - oracle

Question

I'm trying to get the source of a view in my .net app.
To do this, I query DBA_VIEWS: it has a column TEXT with exactly what I need. The type is LONG.
If I do it using the Unmanaged driver, everything works as expected.
The same code with Managed driver results in ORA-01009: missing mandatory parameter.
Adding a transaction around the command and using breakpoint and "slow" steps sometimes results in the same code working.
ODP.NET version is 19, Oracle DB is 18c Express Edition. Strangely enough, the same code works just fine with Oracle Database 12c regardless of driver type.
Is there maybe some setting I need to change on the database or in code? I'm completely lost here.
Code I'm using for testing:
Imports System.Data.Common
Imports Oracle.ManagedDataAccess
'Imports Oracle.DataAccess
Module Views
Function CreateCommand(Connection As DbConnection) As System.Data.Common.DbCommand
Dim cmd As Data.Common.DbCommand = Connection.CreateCommand()
With CType(cmd, Client.OracleCommand)
.BindByName = True
.FetchSize = &H100000 '1 Mb
.InitialLONGFetchSize = -1 'the entire LONG or LONG RAW data is prefetched and stored in the fetch array.
.InitialLOBFetchSize = -1 'the entire LOB data is prefetched and stored in the fetch array.
End With
Return cmd
End Function
Sub query()
Try
Using DBConnection = New Client.OracleConnection("User ID=TESTUSER;Password=TESTPWD;Data Source=TESTDB;Pooling=True")
DBConnection.Open()
Using DBConnection.BeginTransaction()
Using cmdSQL = CType(CreateCommand(DBConnection), Client.OracleCommand)
cmdSQL.CommandText = "select TEXT from DBA_VIEWS where VIEW_NAME = :0"
Dim p = cmdSQL.CreateParameter()
p.ParameterName = "0"
p.Value = "TEST_VIEW"
cmdSQL.Parameters.Add(p)
Dim sw = Stopwatch.StartNew
Using rdr = cmdSQL.ExecuteReader
rdr.FetchSize = 2 ^ 20
While rdr.Read
Dim row(rdr.FieldCount - 1) As Object
rdr.GetProviderSpecificValues(row)
Dim x = row(0)
Console.WriteLine($"{x.ToString.Length} bytes")
End While
End Using
Console.WriteLine($"{sw.ElapsedMilliseconds} ms")
End Using
End Using
End Using
Catch ex As Exception
Console.WriteLine(ex.ToString)
End Try
End Sub
End Module

Answer 1

You can use an anonymous block with output parameter and a call to ExecuteNonQuery. Your command text will be
"begin select TEXT into :0 from DBA_VIEWS where VIEW_NAME = :1; end;"
Add 2 parameters. Make sure that
' Parameter #1 has
p.Direction = ParameterDirection.Output
p.OracleDbType = OracleDbType.Long
p.Size = 1000000
And use command cmd.ExecuteNonQuery(). Then, when parameter is retrieved, just use its value
Dim txt As String = cmd.Parametersp[0].Value.ToString()

Answer 2

It's a pity, Oracle deprecated LONG data type for ages but LONG data is still used many times for internal data.
You could write a function and then get the data by calling the function:
create or replace function GetViewText(v in varchar2) return clob is
ret CLOB;
BEGIN
FOR aRow IN (SELECT TEXT FROM DBA_VIEWS WHERE VIEW_NAME = v) LOOP
ret := aRow.TEXT;
-- or ret := TO_CLOB(aRow.TEXT);
END LOOP;
RETURN ret;
END;

Answer 3

Yet another way from this answer is to (ab)use dbms_xmlgen.getxml.
We can either use it to query a single view's code (as in my original question)
with input as (
select
:0 as VIEW_NAME
from dual
)
SELECT
substr(
text_xml,
instr(text_xml, '<LONGCOL>') + length('<LONGCOL>'),
instr(text_xml, '</LONGCOL>', -1) - (instr(text_xml, '<LONGCOL>') + length('<LONGCOL>'))
) as TEXT
from
(
-- getxml can return malformed xml (which is good in this case)
-- while getxmltype can not.
select dbms_xmlgen.getxml(q'{
SELECT TEXT as LONGCOL
FROM SYS.DBA_VIEWS
WHERE VIEW_NAME = '}' || input.VIEW_NAME || q'{'
}') as text_xml
from input
)
or create our own DBA_VIEWS version.
create or replace view APP_SCHEMA.DBA_VIEWS
as
select
OWNER, VIEW_NAME, TEXT_LENGTH,
case
when (TEXT_VC is not null and TEXT_LENGTH <= 4000)
then to_clob(TEXT_VC)
when TEXT is NULL
then NULL
else (
SELECT
substr(
text_xml,
instr(text_xml, '<LONGCOL>') + length('<LONGCOL>'),
--instr(text_xml, '</LONGCOL>', -1) - (instr(text_xml, '<LONGCOL>') + length('<LONGCOL>'))
TEXT_LENGTH
) as TEXT
from
(
-- getxml can return malformed xml (which is good in this case)
-- while getxmltype can not.
select dbms_xmlgen.getxml(q'{
SELECT TEXT as LONGCOL
FROM SYS.DBA_VIEWS
WHERE OWNER = '}' || OWNER || q'{'
and VIEW_NAME = '}' || VIEW_NAME || q'{'
}') as text_xml
from dual
)
)
end as TEXT,
TEXT_VC, TYPE_TEXT_LENGTH, TYPE_TEXT, OID_TEXT_LENGTH, OID_TEXT, VIEW_TYPE_OWNER, VIEW_TYPE, SUPERVIEW_NAME, EDITIONING_VIEW, READ_ONLY, CONTAINER_DATA, BEQUEATH, ORIGIN_CON_ID, DEFAULT_COLLATION, CONTAINERS_DEFAULT, CONTAINER_MAP, EXTENDED_DATA_LINK, EXTENDED_DATA_LINK_MAP, HAS_SENSITIVE_COLUMN
from sys.dba_views
;