Postgres SQL

From Blue-IT.org Wiki

Revision as of 21:51, 27 October 2013 by Apos (talk | contribs) (→‎Installation)

General

This guide is tested on ubuntu feisty with postgresql 8.2. It should work for former and future versions of both too.

General documentation you will find here:

You should read this in advance to make shure the concepts behind postgresql configuration, startup and security (e.g. 'roles).

User Management

See the excellent online documentation:

Common Tasks

mysql: SHOW DATABASES

postgresql: \l
postgresql: SELECT datname FROM pg_database;

mysql: USE DATABASE

postgresql: \c databsename

mysql: SHOW TABLES

postgresql: \d
postgresql: SELECT table_name FROM information_schema.tables WHERE table_schema = 'public';

mysql: SHOW COLUMNS

postgresql: \d table
postgresql: SELECT column_name FROM information_schema.columns WHERE table_name ='table';


Read more: http://www.linuxscrew.com/2009/07/03/postgresql-show-tables-show-databases-show-columns/#ixzz1DYiUdglU

Ubuntu Feisty, Gutsy, Hardy, ..., Maverick (8.4)

Backup

Also see next section "Upgrade".

From here I have the following idea:

Dump Postgres Database using ssh. Use pg_dump command command: 

pg_dump -U USERNAME YOUR-DATABASE-NAME | \
ssh user@remote.server.com "dd of=/pgsql/$(date +'%d-%m-%y')"

Upgrade - dump and restore

Generally look at

Upgrading from major versions (e.g. 8.1 to 8.3) is done via an database dump/restore cycle:

Dump... 

su postgres
pg_dumpall > /tmp/all.pgsql_81_db.out
pg_dumpall | gzip -c > all.pgsql_81_db.out.gz

and restore... 

psql -f /tmp/all.pgsql_81_db.out postgres

According to this blog entry the following is easy using the cluster upgrade method:pg_upg

"On debian / ubuntu, it's easy to do and there's a command pg_upgradecluster that takes as argument the versions and the locations of the two clusters (a pg installation is called a cluster) and then initdbs the new one like the old one, and initiates a pg_dumpall from the old to the new and voila, you're migrated. Really, it's pretty seamless."

Installation

Install postgresql (version 8.3 for ubuntu hardy / 8.04) 

VER=8.3; sudo apt-get install postgresql-$VER postgresql-client-$VER

If postgesql won't start due to locale settings please do either:

  • edit your SERVER sshd_config file
> vim /etc/ssh/sshd_config 
# Allow client to pass locale environment variables
# AcceptEnv LANG LC_*
  • edit your CLIENT ssh_config file:
> vim /etc/ssh/sshd_config
#    SendEnv LANG LC_*
  • add this at the end of your /etc/profile
> vim /etc/profile 
[...]
export LANGUAGE="en"
export LANG="C"
export LC_MESSAGES="C"

Pgadmin3

Do not use on server environment in the internet, and open the ports to outside access!!! Using VPN and a firewall is no problem.

For administration we install pgadmin3 

sudo apt-get install pgadmin3 pgadmin3-data

Set database admin account

Alter the password for the standard postgres user account (as root) 

sudo su postgres -c psql template1

Inside the database: 

template1=# ALTER USER postgres WITH PASSWORD 'new_password';
template1=# \q

Alter the unix user postgres

sudo passwd -d postgres
sudo su postgres -c passwd

Enable the admin pack for use with pgadmin3

VER="8.3"; sudo apt-get install postgresql-contrib-$VER
sudo su postgres -c psql < /usr/share/postgresql/${VER}/contrib/adminpack.sql

Ubuntu Configuration files

/etc/postgresql/8.2/main/postgresql.conf

Assure that the server is accessible on localhost and from the servers ip. 

VER="8.3"; sudo gedit /etc/postgresql/${VER}/main/postgresql.conf

# - Connection Settings -
# what IP address(es) to listen on; 
# comma-separated list of addresses;
listen_addresses = 'localhost,server_ip'
password_encryption = on

/etc/postgresql/VERSION/main/pg_hba.conf

Security and server settings. If you like to use the server in a network you have to pay attention to three points:

  1. Add the server ip to the listen adress
  2. Allow special clients to connect
  3. Think about using ssl, if you connect through the internet
VER="8.3"; sudo gedit /etc/postgresql/${VER}/main/pg_hba.conf
VER="8.4"; sudo gedit /etc/postgresql/${VER}/main/pg_hba.conf

For Maverick (8.4) the following (and only those are necessary): 

# Connections for all PCs on the subnet
#
# TYPE DATABASE USER IP-ADDRESS IP-MASK METHOD
# e.g. host all all 192.168.0.0/24 md5
# e.g. host all all 192.168.0.10 255.255.255.0 md5
host all all [ip address] [subnet mask] md5

For all other Ubuntu Versions additionally alter the following entries: 

# Allow any user on the local system to connect to any database under
# any user name using Unix-domain sockets (the default for local
# connections).
#
# Database administrative login by UNIX sockets
local all all trust

# TYPE DATABASE USER CIDR-ADDRESS METHOD

# "local" is for Unix domain socket connections only
local all all md5

# IPv4 local connections:
host all all 127.0.0.1/32 md5
# IPv6 local connections:
host all all ::1/128 md5

Restart postgresql

VER="8.3"; sudo /etc/init.d/postgresql-$VER restart

Maverick (8.4): 

VER="8.4"; sudo /etc/init.d/postgresql restart

openSuSE 10.1, 10.3

SuSE oh SuSE ... why not just simply as debian, redhat & Co. ... !?

First I have to mention that it is almost impossible to get a howto on postgresql configuration on openSuSE. But what made me really angry was, that the sample files delivered with opensuse are completely useless to get a running system. E.g. the localisation settings of the server do not default to unicode.

Not even a search at support database of SuSE or Novell's support database gave me ANY useful result. This is really poor. For an example see this thread. Finding an according howto for ubuntu and getting startet with the server and pgadmin was a matter of minutes.

Second it is not good to change the location and content (!) of configuration files from version to version (10.1 -> 10.3) as this is the case! SuSE should follow the example of debian or redhat. A database system is not a playground for such exeriments and really NOT necessary.

Third without any comment: why does postgres on SuSE 10.3 not use utf-8 by default any more as it did on 10.1 !?

One could draw the conclusion, that NOVELL(former SuSE)-users(!) have not much experience with postgresql databases, compared with debian. This is not very appeasing if you consider using this in a sensible environment with the default configuration.

I am sorry to say, but setting up postgresql on a debian/ubuntu system that supported postgres from its beginning might be a better choice not just for inexperienced users.

Installation of postgresql-server

This is easily done via yast or zypper 

zypper install postgresql-server

Administration

Pgadmin III

Pgadmin is good for managing the database server after it is configured and running. The editing of the configuration files should be made by hand - doiing it with pgadmin is a little bit complicated.

  • Install prior to opensuse 10.3
    • via YaST and the guru repository
  • opensuse 10.3 repositories and later do not contain pgadmin any more

Lack of administration module

Later, when you log into the database, pgadmin and try to click on the postgres system database, pgadmin complains about lacking the adminpack contrib module.

There is a package postgresql-contrib that includes additional modules for the server. But the postgres modules have to be configured separately - according to the postgresql documentation.

This is no problem, when working with other databases than postgres!

Post Installation

Start the server for the first time: 

rcpostgresql start

Login as user postgres and alter the table. Instead of using the template1 database like in ubuntu/debian 

su postgres -c psql postgres
postgres=# ALTER USER postgres WITH PASSWORD 'postgres';
ALTER ROLE
postgres=# \q

openSuSE configuration files

Confusing:

  • all configuration files are owned by postgres:postgres and placed in
/var/lib/pgsql/share
  • all sample configuration files are owned by root:root and placed in
/usr/share/postgresql

Copy the /usr/share/postgresql/*.conf.sample files to /var/lib/pgsql/share/*.conf and alter their permissions/owner: 

(SuSE 10.3) cd /var/lib/pgsql/share
(SuSE 10.1) cd /var/lib/pgsql/data

The next is for 10.3 only: 

(suSE 10.3 only !)
cp /usr/share/postgresql/pg_hba.conf.sample pg_hba.conf
cp /usr/share/postgresql/postgresql.conf.sample postgresql.conf
chown postgres:postgres pg_hba.conf postgresql.conf
chmod 600 postgresql.conf pg_hba.conf postgresql.conf

/var/lib/pgsql/share/pg_hba.conf

I edited the pg_hba.conf (the security settings) according to a debian/ubuntu setup. Delete everything in the original file and usethis content: 

vim pg_hba.conf

# TYPE  DATABASE        USER    IP-ADDRESS      IP-MASK         METHOD
local   all             all                                     trust

# Connections for PCs on the subnet. Add a line for each pc or network
# that want's to connect to the server.
# TYPE  DATABASE USER   IP-ADDRESS      IP-MASK         METHOD
#host   all     all     192.168.0.0/24                  trust
#host   all     all     192.168.0.100   255.255.255.255 trust
host    all     all     127.0.0.1       255.255.255.255 trust

Please alter the settings for accessing the database through other pc's of the network accordingly. The server 192.168.0.100 is just a sample! PostgreSQL on openSuSE is not configured for ident authentification method, like in on a debian system.

/var/lib/pgsql/share/postgresql.conf

For the postgres server settings file postgresql.conf alter the file according to the following settings. Don't forget to add you servers ip to the listen_adresses, if you like access your server from the outside. 

vim postgresql.conf

[...]
# Next: ADD YOUR IP, comma separeted list ...
listen_addresses = 'localhost,192.168.0.1'
port = 5432
max_connections = 100
#ssl = on                    # SERVER DOES NOT START WITH 'ON'
password_encryption = on
shared_buffers = 24MB

log_destination = 'stderr'
redirect_stderr = on
#silent_mode = on            # Please UNCOMMENT !!!
log_line_prefix = '%t %d %u '

stats_start_collector = on
stats_row_level = on
autovacuum = on
default_transaction_read_only = off

datestyle = 'iso, dmy'
lc_messages = 'de_DE.UTF-8'
lc_monetary = 'de_DE.UTF-8'
lc_numeric = 'de_DE.UTF-8'
lc_time = 'de_DE.UTF-8'

Open the Firewall Port

If you like to access the server from other pc's add the port number 5432 (opensuse 10.1 & 10.2) or postgresql server to the allowed services. You can do this with YaST.

Add server start to runlevel

After the installation of postgresql-server, it is not started automatically on boot.

Open the runlevel editor in YaST. Choose expert mode and choose to run the server e.g. in the runlevels 2, 3 and 5.

Restart Server

rcpostgresql restart

Now you should be able to connect to the database via localhost and your IP adress (if added in the pg_hba.conf) via pgadmin.

Administration with Pgadmin III

Pgadmin helps you with almost all administration tasks to manage your postgresql databases. From managing user accounts (roles), creating tables, schemes, constraints (e.g. primary keys) to an extended sql editor.

Initial registration with pgAdminIII

To be able to manage your database with pgadmin you have to configure it for the specific server:

Working with pgAdminIII

Queries with pgadminIII

A very good tool for working with the database is the integrated sql query editor of pgadmin. Select the database you want to work with, then you can choose the query tool from the menu.

PostgreSQL queries are case sensitive. So if you specified Uppercase names for columns you have to use them exactly and in quotes. It might be necessary to add the schemata name postfixed by a dot to get a proper query: 

select "Prename" from myscheme."Client";

Press <F5> to start the query.

You can easily save the queries in a file for later reuse.

Backup and restore with pgadminIII

PgadminIII makes it easy to backup your database with or without all the data. Just highlite the database you like to backup and choose the backup option from the main menu.

Retrieved from "https://wiki.blue-it.org/index.php?title=Postgres_SQL&oldid=4700"