As DBA and Architect, Database Tablespace is a most important thing for storage optimization.

In this post, I am sharing my understanding of the PostgreSQL Tablespace.

A tablespace is a defined disk space location for storing the database metadata and user data. The default tablespaces are pg_global and pg_default. The pg_global tablespace is used for shared system catalogs and pg_default is the default for other databases.

Few advantages in short:

Can move important database metadata in a high-speed disk-like SSD Type

Can move important tables and indexes in a high-speed disk-like SSD Type

Can move temp tables and temp indexes in a sperate disk for better performance

Can manage and take the backup very easily

Not require to depend on one single disk block, and even single/default disk block/partition has also size limitation

Create a TABLESPACE:

CREATE TABLESPACE dbrnd LOCATION 'd:\';

Create a new table in specific tablespace:

CREATE TABLE tbl_test(rno int) TABLESPACE dbrnd;

Change the default tablespace:

SET default_tablespace = dbrnd;

Now, try to create another table which will create in newly created tablespace:

CREATE TABLE tbl_test2(rno int);

Check the list of tablespaces:

SELECT spcname FROM pg_tablespace;

In this post, I am sharing a script to check the Tablespace and Filespace information in Greenplum.

In a big database system, DBAs are creating different tablespaces for storage purpose so using below script we can get the information of tablespaces.

SELECT
	spcname as tblspc
	,fsname as filespc
	,fsedbid as seg_dbid
	,fselocation as datadir
FROM pg_tablespace pgts
	,pg_filespace pgfs
	,pg_filespace_entry pgfse
WHERE pgts.spcfsoid=pgfse.fsefsoid
AND pgfse.fsefsoid=pgfs.oid
ORDER BY tblspc, seg_dbid

My Problem:

In our Windows based PostgreSQL Server, We were facing Hard disk related performance issue. Later, we decided to move some of our main tables on SSD Hard Disk (Solid State Drive).

The Performance of SSD Hard drive is 10 times faster than normal HDD Disk.

The Solution:

First, We have to create new Tablespace on SSD disk. The pg_default is a default Tablespace in PostgreSQL. A Tablespace contains all Table information and data.

In PostgreSQL, We can create a new Tablespace or we can also alter Tablespace for existing Tables.
We can perform this exercise using both PGAdmin tool and Script.

In below example, I am creating and changing Tablespace using script.

The Syntax of CREATE TABLESPACE:

CREATE TABLESPACE tablespace_name
OWNER user_name
LOCATION directory_path;

Create a sample Tablespace:

CREATE TABLESPACE dbrnd
OWNER postgres
LOCATION 'E:\temp\dbrnd';

Create a new table under newly created Tablespace:

CREATE TABLE tbl_Students
(Rno INT, Name CHARACTER VARYING)
TABLESPACE dbrnd;

We can also change default Tablespace:
After this change, all your newly table can create under dbrnd Tablespace.

SET default_tablespace = dbrnd;

Create one more table and test this:

CREATE TABLE tbl_Employee
(Eno INT, Name CHARACTER VARYING);

Change Tablespace of existing Table:

ALTER TABLE tbl_Employee SET TABLESPACE pg_default;

Check all Tablespace of your PostgreSQL Database Server:

SELECT spcname FROM pg_tablespace;