Discussion on: PostgreSQL temp files usage

[Bolaji Wahab]

For this part of the query

path ~ ('PG_' || substring(current_setting('server_version') FROM '^(?:\d.\d\d?|\d+)'))

When you create a tablespace, a directory is created in format PG_server_version_some_other_digit.
We check all tablespaces except pg_global for temp files.

For the error "ERROR: absolute path not allowed".

I cannot figure where the error seems to be coming from currently but it seems to be related to tablespace setup.
Are you using tablespaces? And if so, can you confirm the setup of the tablespaces?

Thank you.

[dinesh reddy]

[dinesh reddy]

Anything wrong with the tablespace setup

[Bolaji Wahab]

Can you try break down the query? That way it would be easier to debug.
The first part

WITH tablespaces AS (
    SELECT
        spcname AS tbl_name,
        coalesce(nullif(pg_tablespace_location(oid), ''), (current_setting('data_directory') || '/base')) AS tbl_location
    FROM pg_tablespace
),
tablespace_suffix AS (
    SELECT
        tbl_name,
        tbl_location || '/pgsql_tmp' AS path
    FROM tablespaces
    WHERE tbl_name = 'pg_default'
    UNION ALL
    SELECT
        tbl_name,
        tbl_location || '/' || path || '/pgsql_tmp'
    FROM tablespaces, LATERAL pg_ls_dir(tbl_location) AS path
    WHERE path ~ ('PG_' || substring(current_setting('server_version') FROM '^(?:\d\.\d\d?|\d+)'))
)
SELECT * FROM tablespace_suffix;

[Bolaji Wahab]

Btw, which version of PostgreSQL is it and is it native PostgreSQL?

[dinesh reddy]

Yes native postgresql version is 10.7 on oracle el 6 and query is failing here and when i comment second part after union all error not getting reported then

tablespace_suffix AS (
SELECT
tbl_name,
tbl_location || '/pgsql_tmp' AS path
FROM tablespaces
WHERE tbl_name = 'pg_default'
UNION ALL
SELECT
tbl_name,
tbl_location || '/' || path || '/pgsql_tmp'
FROM tablespaces, LATERAL pg_ls_dir(tbl_location) AS path
WHERE path ~ ('PG_' || substring(current_setting('server_version') FROM '^(?:\d.\d\d?|\d+)'))
),

[dinesh reddy]

[dinesh reddy]

after commenting the second part of union all , am i missing anything

postgres=# WITH tablespaces AS (
postgres(# SELECT
postgres(# spcname AS tbl_name,
postgres(# coalesce(nullif(pg_tablespace_location(oid), ''), (current_setting('data_directory') || '/base')) AS tbl_location
postgres(# FROM pg_tablespace
postgres(# ),
postgres-# tablespace_suffix AS (
postgres(# SELECT
postgres(# tbl_name,
postgres(# tbl_location || '/pgsql_tmp' AS path
postgres(# FROM tablespaces
postgres(# WHERE tbl_name = 'pg_default'
postgres(# --UNION ALL
postgres(# -- SELECT
postgres(# -- tbl_name,
postgres(# -- tbl_location || '/' || path || '/pgsql_tmp'
postgres(# -- FROM tablespaces, LATERAL pg_ls_dir(tbl_location) AS path
postgres(# -- WHERE path ~ ('PG_' || substring(current_setting('server_version') FROM '^(?:\d.\d\d?|\d+)'))
postgres(# )
postgres-# SELECT * FROM tablespace_suffix;
tbl_name | path

------------+---------------------------------------
pg_default | /nfs-mnt/postgres/data/base/pgsql_tmp
(1 row)

[Bolaji Wahab]

Okay. Can you run

SELECT pg_ls_dir('/nfs-mnt/postgres/tablespaces/omnia');

This postgresql.org/docs/10/functions-a.... seems to be the issue but I believe you are using superuser.

[dinesh reddy]

Yes iam using postgres as login user

postgres=# SELECT pg_ls_dir('/nfs-mnt/postgres/tablespaces/omnia');
ERROR: absolute path not allowed
postgres=# \conninfo
You are connected to database "postgres" as user "postgres" via socket in "/var/run/postgresql" at port "5432".

[dinesh reddy]

looks like pg_ls_dir works only on postgresql datadirectory $PGDATA

postgres=# SELECT pg_ls_dir('/nfs-mnt/postgres/data/base');

pg_ls_dir

13457
1
147972689
13456
124079171
(5 rows)

postgres=# SELECT pg_ls_dir('/nfs-mnt/postgres/tablespaces/omnia');
ERROR: absolute path not allowed
postgres=#

[Bolaji Wahab]

Oh yeah. I just confirmed the functions were limited to only the cluster directory and log directory in 9.6, 10. And they were only changed to support files outside cluster directory later from 11.

[Bolaji Wahab]

REF: postgresql.org/docs/release/11.0/#...