Create a text index on multiple tables

Question

I have read the same forum questions a thousand times about doing this and the only thing they show examples of is using multiple columns in one table.
Here is what I have:
create table documents_a
(id number,
text blob);
create table documents_b
(id number,
text blob);
create table documents_c
(id number,
text blob);
I want to be able to do a text search over all three tables on the blob column. I can't use the multi_column_datastore because from what I read this can only be used with one table.
I eventually want to be able to bring up a snippet of the text that contains the keywords and a link to the actual document.
How do I build a text index that includes each blob column from each of the three tables?

Answer 1

OK so I created the materialized view
create materialized view alltabs as
select a.id, a.text, b.id, b.text, c.id, c.text
from tablea a, tableb b, tablec c;
and I created the following
ctx_ddl.create_preference(my_multi', "MULTI_COLUMN_DATASTORE');
ctx_ddl.set_attribute('my_multi','columns','a_document, b_document, c_document');
Then I attempted but I am not sure what column name to put in the pararens?
create index multi_tab on alltabs(????)
indextype is ctxsys.context
parameters('datastore my_multi sync(on commit)');
I saw a dummy column created in most of the internet examples but just exactly what gets created here? I want to create a multi column index so didn't I already tell it which columns up above?