> Cluster Index (or Indexed Views as it's called in SQL Server) is the typical mechanism to sort the data on the disk in RDBMS. MySQL does that by default with the primary key, but not Postgres.
Does that mean that Mysql moves the second or the first half of the table if you insert a row in the middle? I can't imagine that.
I've recently considered clustering multiple tera bytes of time-ordered data stored >100 partitions in a Postgres 12 instance. After careful consideration I came to the conclusion it wasn't worth it. Clustering would have sorted all the rows by date in the table blocks. But that doesn't guarantee anything about the block layer below the filesystem. So it is of dubious value from the standpoint of performance. The other advantage I was hoping for was being able to use a BRIN index. But since, my database has very rare cases of updates of those rows. A BRIN index looses its value very fast. Either I lower the fillrate to leave space in every block for updates. Which allows the BRIN index to stay current but costs a lot of space. Or I would have to force BRIN index updates regularly because they can be lossy. And that is not acceptable in my application. The whole database is stored on nvme disks managed by zfs. That won't benefit from ordering the data on some arbitrary abstraction in the middle.
Does that mean that Mysql moves the second or the first half of the table if you insert a row in the middle? I can't imagine that.
I've recently considered clustering multiple tera bytes of time-ordered data stored >100 partitions in a Postgres 12 instance. After careful consideration I came to the conclusion it wasn't worth it. Clustering would have sorted all the rows by date in the table blocks. But that doesn't guarantee anything about the block layer below the filesystem. So it is of dubious value from the standpoint of performance. The other advantage I was hoping for was being able to use a BRIN index. But since, my database has very rare cases of updates of those rows. A BRIN index looses its value very fast. Either I lower the fillrate to leave space in every block for updates. Which allows the BRIN index to stay current but costs a lot of space. Or I would have to force BRIN index updates regularly because they can be lossy. And that is not acceptable in my application. The whole database is stored on nvme disks managed by zfs. That won't benefit from ordering the data on some arbitrary abstraction in the middle.