News for hackers. Stuff that matters.

A comment on Pgroll: zero-downtime, undoable, schema migrations for Postgres. Parent comment

Re:Pgroll: zero-downtime, undoable, schema migrations for Po... by vlovich123 on Tuesday October 03, 2023 @05:39PM (#37757931)
Is my understanding correct that the need to copy columns makes starting a migration potentially extremely expensive on a large database?
[ Parent | on HN ]
Re:Pgroll: zero-downtime, undoable, schema migrations for Po... by surjection on Tuesday October 03, 2023 @05:51PM (#37758084)
Yes, for those pgroll migrations that require a new column + backfill, starting the migration can be expensive.

Backfills are done in fixed size batches to avoid long lived row locks, but the operation can still be expensive in terms of time and potentially I/O. Options to control the rate of backfilling could be a useful addition here but they aren't present yet.

[ Parent | on HN ]