Hi team, I have a table with a column of "timestamp without timezone" and I want to alter it to a column of "timestamp with timezone" without rewriting the rows.
Looking at the docs, and doing some quick tests, the data-on-disk is identical for both columns. But when doing an alter table, looks like it's rewriting the rows: (PostgreSQL 13.1) guru=# create table tt(m timestamp without time zone default now()); guru=# insert into tt(m) values(now()); guru=# SELECT xmin, xmax, cmin, cmax, m from tt; xmin | xmax | cmin | cmax | m ------+------+------+------+---------------------------- 695 | 0 | 0 | 0 | 2021-01-13 11:47:59.146952 (1 row) guru=# alter table tt alter column m type timestamp with time zone; guru=# SELECT xmin, xmax, cmin, cmax, m from tt; xmin | xmax | cmin | cmax | m ------+------+------+------+------------------------------- 696 | 0 | 4 | 4 | 2021-01-13 11:47:59.146952+01 (1 row) Is there any reason to rewrite the rows or is it just an optimization that no one hasn't sent a patch ? Regards, Dorian
