equivalence class not working?

not sure if this is the right place to post...

 

I am using postgres 8.1.  In indxpath.c, it says " Note: if Postgres tried to optimize queries by forming equivalence
classes over equi-joined attributes (i.e., if it recognized that a qualification such as "where a.b=c.d and a.b=5" could make use of
 an index on c.d), then we could use that equivalence class info here with joininfo_list to do more complete tests for the usability
of a partial index.  .....  XXX as of 7.1, equivalence class info *is* available."

 

 

Now i have the following two queries on TPC-H, where there is an index built on "o_totalprice".

 

explain select * from lineitem, orders where o_totalprice=l_extendedprice and l_extendedprice<2000;

explain select * from lineitem, orders where o_totalprice=l_extendedprice and l_extendedprice<2000 and o_totalprice<2000;

 

The second query uses the index while the first does not. It seems to me that both queries are the same (the "o_totalprice<2000" in the second query can be inferred).    Is there something that needs to be tuned or ...?

 

thanks a lot!