Text index getting dropped on SET NULL?

Question

I am using Oracle 11g2 XE. With the following text index settings:
ctx_ddl.create_preference('wrld_lexer', 'WORLD_LEXER');
ctx_ddl.create_preference('TextIDX_preference', 'MULTI_COLUMN_DATASTORE');
ctx_ddl.set_attribute('TextIDX_preference', 'columns', '"dummy", "FieldVarChar2", "FieldCLOB"');
ctx_ddl.create_preference('wrdlist', 'BASIC_WORDLIST');
ctx_ddl.set_attribute('wrdlist','PREFIX_INDEX','TRUE');
ctx_ddl.set_attribute('wrdlist','PREFIX_MIN_LENGTH', '1');
ctx_ddl.set_attribute('wrdlist','PREFIX_MAX_LENGTH', '15');
ctx_ddl.set_attribute('wrdlist','SUBSTRING_INDEX', 'YES');
ctx_ddl.set_attribute('wrdlist','WILDCARD_MAXTERMS', 5000) ;
ctx_ddl.create_stoplist('universal_stoplist','BASIC_STOPLIST');
CREATE INDEX TextIDX ON "TextTable"("dummy")
    INDEXTYPE IS CTXSYS.CONTEXT PARAMETERS
     ('DATASTORE ME.TextIDX_preference LEXER ME.wrld_lexer WORDLIST ME.wrdlist STOPLIST ME.universal_stoplist FILTER CTXSYS.AUTO_FILTER SYNC (ON COMMIT)');The "FieldCLOB" is a nullable CLOB field is quite volatile. I have a task scheduled in Oracle to execute a stored procedure that first sets the whole column to NULL and afterwards inserts a bunch of text, ranging from a couple of words to over 4000 characters. It seems that whenever that stored procedure is called, afterwards my search engine can't find a thing! When I drop and create the index, it works again.. to a degree. It seems that the text index doesn't want to search on the FieldCLOB. It ignores it.
Why is that so?
I should note that I am fairly new to Oracle and I don't really know where to begin on this problem.

Answer 1

I knew I've forgotten to add something to the question.
The thing is that I am aware of that and I do have the trigger defined:
create or replace
trigger Text_trigger
before update on "TextTable"
for each row
begin
  :new."dummy" := :new."dummy";
end;This has worked in the past, but it seems that the changes I've made to the scheduled procedure drops the whole index or something. Here is my sproc:
UPDATE "TextTable"
SET "FieldCLOB" = NULL;
commit;
FOR pair IN (select "Find", "Append" from "Table1")
LOOP          
  update "TextTable"
  set "FieldCLOB" = "FieldCLOB" || pair."Append"
  where ID in
     (select ID from "TextTable"
     where contains("dummy", pair."Find") > 0);
  commit;
END LOOP;
-- The problems started when I added this to the scheduled procedure:
FOR pair IN (select "Find", "Append" from "Table2")
LOOP          
  update "TextTable"
  set "FieldCLOB" = "FieldCLOB" || pair."Append"
  where ID in
     (select ID from "TextTable"
     where contains("dummy", pair."Find") > 0);
  commit;
END LOOP;Edited by: 981243 on Mar 8, 2013 2:20 AM