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http://rhaas.blogspot.com/2011/02/mysql-vs-postgresql-part-2-vacuum-vs.html http://rhaas.blogspot.com/2011/02/mysql-vs-postgresql-part-2...
by homebrewer 2y ago
http://rhaas.blogspot.com/2011/02/mysql-vs-postgresql-part-2-vacuum-vs.html http://rhaas.blogspot.com/2011/02/mysql-vs-postgresql-part-2...
- sudhirj 2y agoThat helps a lot thanks. Will summarize it quickly for those who come later: MySQL (InnoDB really) and Postgres both use MVCC, so they write a new row on update. InnoDB however also additionally writes a record marking the old row for deletion. To do a cleanup, InnoDB uses the records it kept to delete old data, while Postgres must do a scan. So InnoDB pays a record-keeping price as part of the update that makes it easier to clear data, while Postgres decides to pay this price of occasional scanning.