OK, so let me summarize here (the other posts in this subthread are
discussing the user interface, not the use cases, so I'll respond here).


There are two main use cases:

1) change the order of columns in "SELECT *"

   - display columns so that related ones grouped together
     (irrespectedly whether they were added later, etc.)

   - keep columns synced with COPY

   - requires user interface (ALTER TABLE _ ALTER COLUMN _ SET ORDER _)


2) optimization of physical order (efficient storage / tuple deforming)

   - more efficient order for storage (deforming)

   - may be done manually by reordering columns in CREATE TABLE

   - should be done automatically (no user interface required)

   - seems useful both for on-disk physical tuples, and virtual tuples


Anything else?

-- 
Tomas Vondra                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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