On 12/9/14 12:41 PM, Alvaro Herrera wrote: > To recap, this is based on the idea of having three numbers for each > attribute rather than a single attnum; the first of these is attnum (a > number that uniquely identifies an attribute since its inception and may > or may not have any relationship to its storage position and the place > it expands to through user interaction). The second is attphysnum, > which indicates where it is stored in the physical structure. The third > is attlognum, which indicates where it expands in "*", where must its > values be placed in COPY or VALUES lists, etc --- the logical position > as the user sees it.
Side idea: Let attnum be the logical number, introduce attphysnum as the storage position, and add an oid to pg_attribute as the eternal identifier. That way you avoid breaking pretty much all user code that looks at pg_attribute, which will probably do something like ORDER BY attnum. Also, one could get rid of all sorts of ugly code that works around the lack of an oid in pg_attribute, such as in the dependency tracking. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
