Hello there. I read http://www.postgresql.org/docs/current/static/sql-altertable.html and find it interesting that " Adding a column with a non-null default or changing the type of an existing column will require the entire table to be rewritten. This might take a significant amount of time for a large table; and it will temporarily require double the disk space." So adding a new column WITHOUT any default value is actually a quite cheap operation then? Some quick tests seem to indicate that. So if you can live with having a null values there until the value is set (or you let a cron job run and set the value to a desired "default value" for one row at a time), then adding columns will not be a real problem? No serious locking for a long time? And droping a column seems even quicker "The DROP COLUMN form does not physically remove the column, but simply makes it invisible to SQL operations. Subsequent insert and update operations in the table will store a null value for the column. Thus, dropping a column is quick but it will not immediately reduce the on-disk size of your table, as the space occupied by the dropped column is not reclaimed. The space will be reclaimed over time as existing rows are updated. " So that is really quick then? Will autovaccum or other tools try to rewrite or "be clever " and optimize and causing a total rewrite of the table? Any other problems with adding/dropping columns that I'm unaware of? Best wishes. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
