a couple of ideas

As I was playing around with prelimiary stuff for regression testing the 
CSV patch, I had a couple of ideas I thought I might float.

Context: many of the tests will write a table out and read it back into 
a duplicate table and then perform a symmetric difference on the 2 
tables. Making the query for this is slightly error prone, so I made two 
functions, one to generate the query in text, and the other perform the 
query and return a set of records.

Idea 1: an eval facility for psql. e.g.:
 \eval symdiffgen('foo','bar')

or
 \eval select symdiffgen('foo','bar')

This would be a use of the first query. In effect we'd be providing for 
a sort of macro facility.

Idea 2: allow a LIKE clause in the column specs where a function 
returning a set of records is called. e.g., instead of
 select * from symdiff('foo','bar') as diff(_table_name_ text, d date, 
x text);

allow
 select * from symdiff('foo','bar') as diff(_table_name_ text, like foo);

There may be good reasons not to do either of these, so I am just 
floating them for discussion.

I might also have missed something obvious that would let me do things 
easily some other way.

cheers

andrew