"David G. Johnston" <david.g.johnston@xxxxxxxxx> writes: > On Thu, Jul 28, 2022 at 8:13 AM Ron <ronljohnsonjr@xxxxxxxxx> wrote: >> Besides what's mentioned in >> https://www.postgresql.org/docs/12/ddl-alter.html#id-1.5.4.8.10, what >> happens *internally* when I run: >> ALTER TABLE foo ALTER COLUMN bar TYPE BIGINT; > IIUC, that would be the silver lining in all of this - the rewritten table > would have zero fragmentation and bloat. Yeah. What happens internally is a table rewrite: the entire content of the table (and its indexes) is written into a new set of files. At commit, the old files are deleted. The main gotchas, for a large table, are the transient disk space consumption and the fact that the table stays exclusively locked the whole time. regards, tom lane
