Even if I have a lot of free space PgSQL returns "ERROR: could not extend file - No space left on device"

[Nature Conservation Geovista Space <conservation.by.geovista.space@xxxxxxxxx>]

Dear Pg-users,

I am coming back to Postgres/PostGIS after a few years. I am dealing with a big database with a lot of geometries and too many vertices.

After hours running a query to Subdivide, I get this Postgres error

2023-09-08 02:11:23.745 BST [328594] postgres@database ERROR:  could not extend file "base/16388/7985375.1020": No space left on device
2023-09-08 02:11:23.745 BST [328594] postgres@database HINT:  Check free disk space.

2023-09-08 02:11:23.745 BST [328594] postgres@database  STATEMENT:  CREATE TABLE _gaul_administrative_subdivided100 AS (
                SELECT *, st_subdivide(geom,100) AS geom_subdivided100
                        FROM gaul_administrative
        );

2023-09-08 02:15:38.251 BST [313729] LOG:  checkpoint complete: wrote 81956 buffers (1.6%); 0 WAL file(s) added, 0 removed, 608 recycled; write=269.414 s, sync=0.001 s, total=269.634 s; sync files=1, longest=0.001 s, average=0.001 s; distance=9962549 kB, estimate=9980351 kB; lsn=291/BF46ABE8, redo lsn=291/A0FB7D98

It seems that it is not a problem of space.

Command df -h returns:

Filesystem      Size  Used Avail Use% Mounted on
tmpfs           6.3G  1.1M  6.3G   1% /run
/dev/sda        1.3T  164G  1.1T  14% /
tmpfs            32G  3.2M   32G   1% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           6.3G  4.0K  6.3G   1% /run/user/1000

Command df -ih returns:

Filesystem     Inodes IUsed IFree IUse% Mounted on                                                                                
tmpfs            7.9M   724  7.9M    1% /run                                                                                      
/dev/sda          80M  179K   80M    1% /                                                                                         
tmpfs            7.9M     4  7.9M    1% /dev/shm                                                                                  
tmpfs            7.9M     3  7.9M    1% /run/lock                                                                                 
tmpfs            1.6M    28  1.6M    1% /run/user/1000

I suppose it is an issue with temporary table, here my present configuration in postgresql.conf

#temp_tablespaces = ''                  # a list of tablespace names, '' uses                                                     
                                        # only default tablespace   

#temp_file_limit = -1                   # limits per-process temp file space                                                      
                                        # in kilobytes, or -1 for no limit   

What do you suggest?

cheers,

Enzopolo