[fuy]

CLUSTER command is not the same as index organized tables, it's a one-time "physical sort" operation. New data is not organized until you run CLUSTER again. Index organized tables are maintained automatically by Oracle/SQL Server.

[SigmundA]

Not just maintained automatically, clustered indexes have no heap at all, the table is an index.

The CLUSTER command in PG just moves rows around in the heap so they match the still separate index order which can help a little bit with range operations because rows are close on disk, but otherwise doesn't do much.

So they are completely separate things that just happen to use the same term.

[wreath]

Interesting, i didnt know that. Thanks!