all_ind_expressions view of Oracle

Question

I'm trying to execute the below query through OracleDataReader in .NET but when I try to read the value of the column_expressions column, I always get an empty string.

SELECT ic.column_name,
       ie.column_expression
 FROM all_ind_columns ic
 LEFT JOIN all_ind_expressions ie
   ON ie.index_owner     = ic.index_owner
  AND ie.index_name      = ic.index_name
  AND ie.column_position = ic.column_position
WHERE ic.index_owner     = 'owner_name'
  AND ic.index_name      = 'index_name'

I realized that the datatype of the column id is LONG but I'm not sure if that's the reason. Is there a way I can read the actual value of the column?

When I execute the same query through Oracle SQL developer, I can see the value.

Answer 1

To be able to read a column that is of LONG data type the InitialLONGFetchSize property of OracleCommand has to be set to a none zero(zero by default) value:

Unfortunately you did not provide your .NET code, so I'll give you a C# + ODP.NET unmanaged driver example:

Set-up:

create table t1(
  col1 varchar2(11)
);

create index FBI on t1(upper(col1));

table T1 created.
index FBI created.

C# code:

string oraConnectionString = "Data source=nkpdb;User id=hr;password=password;";
OracleConnection oraConnection = new OracleConnection(oraConnectionString);
oraConnection.Open();
/* Would be better to put this in a stored procedure */      
string sqlQuery = "select ic.column_name "  +
                  "     , ie.column_expression " +
                  "  from all_ind_columns ic " +
                  "  left join all_ind_expressions ie " +
                  "    on ie.index_owner      = ic.index_owner " +
                  "   and ie.index_name      = ic.index_name " +
                  "   and ie.column_position = ic.column_position " +
                  " where ic.index_owner   = :INDOwner " +
                  "   and ic.index_name    = :INDName" ;
OracleCommand oraCmd     = new OracleCommand(sqlQuery, oraConnection);
OracleParameter indOwner = new OracleParameter("INDOwner", 
                                                OracleDbType.Varchar2);
OracleParameter indName  = new OracleParameter("INDName", 
                                                OracleDbType.Varchar2);
indOwner.Value = "HR";
indName.Value = "FBI";
oraCmd.Parameters.Add(indOwner);
oraCmd.Parameters.Add(indName);
/* set up initial amount of data that the OracleDataReader 
 * fetches for LONG column */
oraCmd.InitialLONGFetchSize = 1000;  /* set initial size */ 
OracleDataReader oraDataReader = oraCmd.ExecuteReader();
if (oraDataReader.HasRows)
{
     while (oraDataReader.Read())
     {
       Console.WriteLine(oraDataReader.GetString(
                               oraDataReader.GetOrdinal("column_expression")));
      }
 }

Result:

By default the InitialLONGFetchSize property is set to 0. That's the reason why you are getting an empty string. So you either need to set this property to a value greater than zero or set it to -1 to fetch an entire LONG column.

Answer 2

Here 's another simple solution.

1 - Create this function

    create or replace function Get_Text
    (sINDEX_NAME in VARCHAR2, sIndex_owner in VARCHAR2, sColumn_position in VARCHAR2) 
    return varchar2
is
    Long_to_Varchar        varchar(32767);
begin
    select  COLUMN_EXPRESSION into Long_to_Varchar
        from SYS.all_ind_expressions 
        where INDEX_NAME = sINDEX_NAME and Index_owner=sIndex_owner and Column_position=sColumn_position;
    return long_to_varchar;
exception
    when others then
        return 'Error occurred';
end;

2 - Use this SQL

   select ic.index_name, 
       ic.column_name,
       GET_TEXT(Ie.INDEX_NAME,Ie.Index_owner,ie.Column_position )
from all_ind_columns ic
  left join all_ind_expressions ie 
    on ie.index_owner = ic.index_owner
   and ie.index_name = ic.index_name
   and ie.column_position = ic.column_position
WHERE ic.index_owner     = 'owner_name'
  AND ic.index_name      = 'index_name'