Oracle datapump metadata_filter

In Oracle I want to export tables using dbms_datapump. I have a table containing a list of table names that I want to export a subset of, where the grp = 'batch1'. I want to loop through each of those table names and pass the table name over to the metadata_filter. However it's not working. I specifically want to do this in a loop.

Here are some extracts from the code:

CURSOR lib_cur IS
     SELECT table_name
                   FROM my_table_list
                   WHERE grp = 'batch1';

Later on in the code:

for x in lib_cur
    LOOP

     table_nm := x.table_name;

    dbms_datapump.metadata_filter          
    (handle      => my_job_handle,      
     name        => 'NAME_EXPR', 
     value       => 'IN (''' || table_nm || ''')' ,
     object_type => null); 

Does anyone know why this isn't passing the current value of table_nm over to the value parameter of dbms_datapump.metadata_filter? If I hardcode one of the actual table names in that I want e.g. ''table1'' it works fine.

I know that my loop is bringing the correct table names into the table_nm variable as I've output them to dbms_output and can see that with each iteration of the loop comes a different table name.

So any ideas why the name isn't being passed across in my Loop? I don't know if the syntax is incorrect or if it's just not possible to do it this way? The thing is I'm sure I had it working a while ago!

You are replacing the filter each time in your loop. You want to provide the entire list at once. Try using LISTAGG to assemble a delimited list of tables into a single scalar variable that you can pass to the filter:

SELECT 'IN ('''||LISTAGG(table_name,''',''') WITHIN GROUP (ORDER BY 1)||''')'
  INTO var_table_list
  FROM my_table_list
 WHERE grp = 'batch1';

 dbms_datapump.metadata_filter          
    (handle      => my_job_handle,      
     name        => 'NAME_EXPR', 
     value       => var_table_list,
     object_type => null);