Hi . Apology for the bandwith. Did not know who to ask the question . I was interested in a brief detail on how postgress does expression pruning between nodes . The basic question is as follows
Scenerio In a plan where Node 1 is parent {say join) and Node 2 is child (say scan) . If node 1 has a expression say foo(column) then scan will project 'column' for sure and join will evaluate foo(column). Now if the node above join does not need column ? how does postgress remove the column from join's projection list . I am seeing that it does not in many cases specially when sort appears above. Question In general is there something in the code that can process a plan tree and find out where expressions are generated and where there references are not required - thus removing expressions not needed . In my case the column is a huge column and hence it will matter if it is removed from the projection list as soon as possible ? Any insights welcome and thanks for all help Regards Harmeek -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers