how does trino compaction work

[JunseoChoJJ]

@findepi
I had 371 parquet file it's about 500kb each and total 240mb
and I compact using trino statement

alter table nessie_catalog.nessie.kafka2 execute optimize(file_size_threshold => '128MB')

and I got 3 parquet file. 85mb, 60mb, 45mb
I wonder if I use that statement above I would get 128mb, 60mb just two parquet file

how does trino compaction work?

[findepi]

Exact file size is not guaranteed, as Trino does not aim to create minimal number of files.
This is also subject to writer scaling.