Bug in Oracle Text?

Question

I'm being presumptuous, but:
SQL> drop table foo
Table dropped.
SQL> create table foo (
id NUMBER,
mystring VARCHAR2(1))
Table created.
SQL> insert into foo (id,mystring) values (1,'A')
1 row created.
SQL> insert into foo (id,mystring) values (2,'B')
1 row created.
SQL> insert into foo (id,mystring) values (3,'C')
1 row created.
SQL> insert into foo (id,mystring) values (4,'D')
1 row created.
SQL> insert into foo (id,mystring) values (5,'E')
1 row created.
SQL> commit
Commit complete.
SQL> BEGIN
CTX_DDL.DROP_PREFERENCE('FOO_LEXER');
END;
PL/SQL procedure successfully completed.
SQL> BEGIN
CTX_DDL.CREATE_PREFERENCE('FOO_LEXER','BASIC_LEXER');
CTX_DDL.SET_ATTRIBUTE('FOO_LEXER','BASE_LETTER','YES');
END;
PL/SQL procedure successfully completed.
SQL> CREATE INDEX foo_index ON foo(mystring)
INDEXTYPE IS CTXSYS.CONTEXT
PARAMETERS('lexer foo_lexer')
Index created.
SQL> select *
from foo
where contains(mystring,'A') > 0
no rows selected
SQL> select *
from foo
where contains(mystring,'B') > 0
ID M
2 B
1 row selected.
SQL> select *
from foo
where contains(mystring,'c') > 0
ID M
3 C
1 row selected.
SQL> select *
from foo
where contains(mystring,'d') > 0
ID M
4 D
1 row selected.
SQL> select *
from foo
where contains(mystring,'E') > 0
ID M
5 E
1 row selected.
It only fails for the letter 'A'!

Answer 1

This is actually because 'A' is a stopword. This is expected.
Try doing:
Select token_text from DR$[index_name]$I;
and you will not find the letter 'A' indexed.
Try doing:
select spw_stoplist, spw_word from ctx_stopwords order by 1, 2;
You should see something like:
SPW_STOPLIST SPW_WORD
DEFAULT_STOPLIST Mr
DEFAULT_STOPLIST Mrs
DEFAULT_STOPLIST Ms
DEFAULT_STOPLIST a
DEFAULT_STOPLIST all
DEFAULT_STOPLIST almost
DEFAULT_STOPLIST also
DEFAULT_STOPLIST although
DEFAULT_STOPLIST an
DEFAULT_STOPLIST and
DEFAULT_STOPLIST any
DEFAULT_STOPLIST are
.