Thread: change attnum in pg_catalog.pg_attribute
Welcome I want to change column order in select * from table instruction; I can do that changing attnum but I don't know it is safely or not for system. Question is can do that or not. Thanks for help Best Regards
somee <grzegorz.przezdziecki@polskiesklepy.pl> writes:
> I want to change column order in select * from table instruction;
> I can do that changing attnum but I don't know it is safely or not for
> system.
It won't work and will likely crash the backend.
regards, tom lane
Dnia wtorek, 5 kwietnia 2005 20:13, Tom Lane napisał: > somee <grzegorz.przezdziecki@polskiesklepy.pl> writes: > > I want to change column order in select * from table instruction; > > I can do that changing attnum but I don't know it is safely or not for > > system. > > It won't work and will likely crash the backend. > Even if I will do like this and for ever?? 1. attnum will be unique and greater than 0 2. no holes in attnum numeric 3. Make change 4. restart postgresql > regards, tom lane Best Regards -- Grzegorz Przeździecki www.PolskieSklepy.pl kom. +48.606.822.506 gg:3701851 skype: grzegorz.przezdziecki
Grzegorz =?iso-8859-2?q?Prze=BCdziecki?= <Grzegorz.Przezdziecki@PolskieSklepy.pl> writes:
>> It won't work and will likely crash the backend.
> Even if I will do like this and for ever??
> 1. attnum will be unique and greater than 0
> 2. no holes in attnum numeric
> 3. Make change
> 4. restart postgresql
Yes, unless you also TRUNCATE the table, because attnum ordering tells
about the physical data layout within the table rows. Furthermore,
altering only pg_attribute is unlikely to represent a complete update
of the catalogs --- attnums also show up in pg_index, pg_attrdef,
pg_depend, pg_rewrite if there are any rules or views mentioning the
columns, and probably some other places I forgot.
regards, tom lane
Welcome > > Yes, unless you also TRUNCATE the table, because attnum ordering tells > about the physical data layout within the table rows. Furthermore, > altering only pg_attribute is unlikely to represent a complete update > of the catalogs --- attnums also show up in pg_index, pg_attrdef, > pg_depend, pg_rewrite if there are any rules or views mentioning the > columns, and probably some other places I forgot. > Now understand Thanks a lot > regards, tom lane Best Regards -- Grzegorz Przeździecki www.PolskieSklepy.pl kom. +48.606.822.506 gg:3701851 skype: grzegorz.przezdziecki
Tom Lane <tgl@sss.pgh.pa.us> writes: > somee <grzegorz.przezdziecki@polskiesklepy.pl> writes: > > I want to change column order in select * from table instruction; > > I can do that changing attnum but I don't know it is safely or not for > > system. > > It won't work and will likely crash the backend. Out of curiosity, would it work if the table were completely empty at the time? -- greg