Postgresql:query for location of global tablespace?

Q:

I have been trying to make we database clients pro-active about not filling up the partition on which the database they a Re using resides.

As all of our clients is on the same host as the database manager, it should is easy enough for user-created tablespaces; The client can look up the filesystem path for the tablespace (in spclocation), and use OS calls to check how much Availab Le Space is available:

adb= Select *  fromPg_tablespace; Spcname|Spcowner|Spclocation|Spcacl------------+----------+-------------------+---------------------Pg_default|       Ten |                   |Pg_global|       Ten |                   |adb|  2033793 | /Database /adb|{adb=C/adb

I can ' t see how, from the client, to get the path to where the global tablespace is stored; An empty string was returned for it in the above query.

Unfortunately, we have many legacy systems on the field using a particular database created in the global Tablespace, and It would is a monumental effort to get it moved into a user-created tablespace.

Hopefully I ' m just missing something really simple. A:

Pg_default and Pg_global locations are "hardcoded".

Pg_default lives in:

Test=Select Setting| | ' /base '  from where name='data_directory';

and Pg_global lives in: 

Test=Select Setting| | ' /global '  from where name='data_directory'

src/backend/commands/tablespace.cSays so:   *There is tablespaces created at Initdb time  :Pg_global ( forshared   *Tables )and Pg_default ( foreverything Else ).For backwards compatibility   *And to remain functional on platforms without symlinks ,these tablespaces   *is accessed specially :they is respectively   *$PGDATA /Global /Relfilenode   *$PGDATA /Base /dboid  /Relfilenode   here is the detailed description in the code:
 * Tablespaces in PostgreSQL is designed to allow users to determine
* Where the data file (s) for a given database object reside on the file
* System.
*
* A tablespace represents a directory on the file system. At tablespace
* Creation time, the directory must be empty. To simplify things and
* Remove the possibility of having file name conflicts, we isolate
* files within a tablespace into database-specific subdirectories.
*
* To-Support file access via the information given in Relfilenode, we
* Maintain a Symbolic-link map in $PGDATA/pg_tblspc. The symlinks is
* Named by Tablespace OIDs and point to the actual tablespace directories.
* There is also a Per-cluster version directory of each tablespace.
* Thus the full path to a arbitrary file is
* $PGDATA/pg_tblspc/spcoid/pg_majorver_catver/dboid/relfilenode
* e.g.
* $PGDATA/pg_tblspc/20981/pg_9.0_201002161/719849/83292814
*
* There is tablespaces created at Initdb Time:pg_global (for shared
* tables) and pg_default (for everything else). For backwards compatibility
* and to remain functional on platforms without symlinks, these tablespaces
* is accessed Specially:they is respectively
* $PGDATA/global/relfilenode
* $PGDATA/base/dboid/relfilenode
*
* To allow CREATE database to give a new database a default tablespace
* That's different from the template database ' s default and we make the
* Provision that a zero in pg_class.reltablespace means the database ' s
* Default tablespace. Without this, CREATE DATABASE would has to go
* and munge the system catalogs of the new database.
*
Reference:Http://dba.stackexchange.com/questions/9603/postgresql-query-for-location-of-global-tablespacesrc/backend/commands/tablespace.c

Postgresql:query for location of global tablespace?