sqlite3 - Why does SQLite not use an index when using a literal column value in the WHERE clause? -

here's sqlfiddle of example, let me explain:

when have simple table this:

create table forgerock     (`id` int, `productname` varchar(7), `description` varchar(55)) ; 

and simple index on productname column this:

create index test_idx on forgerock(productname); 

i can select data using productname in clause , index being used. nice.

when add hard-coded value list of columns i'm selecting, works , index used, too:

select   0 foo,   0 bar,   productname,   description   forgerock (foo = 0 , productname in ('openidm', 'opendj')) 

even using hard-coded foo column in clause still uses index (as should). here's question: why index not being used when add or (foo = 1 , bar in (1)) clause?

select   0 foo,   0 bar,   productname,   description   forgerock (foo = 0 , productname in ('openidm', 'opendj')) or (foo = 1 , bar in (1));  

any appreciated. once again, here's sqlfiddle.

the documentation says:

where clause constraints connected or instead of , can handled [...]
given query, fact or-clause optimization described here can used not guarantee used. sqlite uses cost-based query planner estimates cpu , disk i/o costs of various competing query plans , chooses plan thinks fastest. if there many or terms in clause or if of indices on individual or-clause subterms not selective, sqlite might decide faster use different query algorithm, or full-table scan.