Thanks Peter for your answer,
On 20/06/2022 17:47, Peter Geoghegan wrote:
>
> Yes, this is expected. Parallel CREATE INDEX performs its parallel
> sort by having workers generate sorted runs, which are written to temp
> files, and then having the leader process merge the sorted runs
> together as the index is built.
Just to make sure we are on the same page: every parallel 'CREATE INDEX' writes to temp files, ok.
But why the temp files are always on disk and not in RAM as other operations do?
> In the case where there is amble maintenance_work_mem, all writes to
> and reads from temp files will be sequential.
>