Got following answer,
http://dba.stackexchange.com/questions/69411/postgresql-partition-pruning/69413#69413
--View this message in context: http://postgresql.1045698.n5.nabble.com/How-does-the-PostgreSQL-partition-pruning-happens-tp5809921p5809923.htmlSent from the PostgreSQL - general mailing list archive at Nabble.com.