private-schrijfsels-en-notities/2024/Postgres Backups and ZFS snapshots.md

• 3485292005/pkg/postgres/postgres.go
• Quiesce & Unquiesce terminology
• https://zrepl.github.io/v0.2.1/configuration/snapshotting.html#postgres-checkpoint-hook
• https://www.postgresql.org/docs/16/wal-reliability.html
• https://www.postgresql.org/docs/15/functions-admin.html

func takeSnapshot(db *sql.DB, dataset string, height int, tag string) error {
	log.Printf("Taking a ZFS snapshot: %s@%d%s", dataset, height, tag)
	log.Printf("  calling pg_backup_start('blkchain', true)") // pg < 15 use pg_start_backup
	if _, err := db.Exec(`SELECT pg_backupstart('blkchain', true)`); err != nil {
		return err
	}
	log.Printf("  executing COPY (SELECT) TO PROGRAM 'zfs snapshot %s@%d%s'", dataset, height, tag)
	if _, err := db.Exec(fmt.Sprintf(`COPY (SELECT) TO PROGRAM 'zfs snapshot %s@%d%s'`, dataset, height, tag)); err != nil {
		return err
	}
	log.Printf("  calling pg_backup_stop()") // pg < 15 use pg_stop_backup
	if _, err := db.Exec(`SELECT pg_backup_stop()`); err != nil {
		return err
	}
	return nil
}