[GENERAL] to know what columns are getting updated

[Sajeev Mayandi]

Hi,

I have bunch of rules created for tables to implement upsert functionality.     
 My problem is our tables gets updated from multiple places ,  non –necessarily 
with the same no of columns. I want to figure out  columns are being asked to 
be updated

E.g. The rule for the the table base-table is

CREATE OR REPLACE RULE base-table-rule  AS
    ON INSERT TO base-table
   WHERE (EXISTS ( SELECT 1
           FROM base-table
          WHERE bas-table::x1 = new.x1  ))
      DO INSTEAD  UPDATE base-table  SET x1=new.x1,x2=new.x2,x3 
=new.x3,x4=new.x4
  WHERE base-table.x1= new.x1;



1) user 1 comes with the below insert
 Insert into base-table(x1,x2,x3,x4) values(v1,v2,v3,v4);

2) user 2 comes with the below insert
Insert into base-table(x1,x2) values(v1,v2);

Since user 2 uses only x1 and x2 as its column the rule replaces x3 and x4 with 
null.

Is there a way to figure out that only x1 and x2 is being asked for an 
updating. In the above example column x1 is the primary key.

Thanks,

Sajeev