Gravi80 / DataBase_fundas

DataBase_fundas

all queries are written only for postgres database.

Interesting Articles:

http://patshaughnessy.net/2014/10/13/following-a-select-statement-through-postgres-internals

http://patshaughnessy.net/2014/11/11/discovering-the-computer-science-behind-postgres-indexes

http://blog.tarkalabs.com/2015/04/16/managing-big-enough-data-in-postgres/

INSATLL POSTGRES

[kelvin@schettino ~]$ sudo yum install postgresql-server

Configure Postgres – Initialize and start service

kelvin@schettino ~]$ sudo service postgresql initdb

Set the server to restart on reboots and start the postmaster service:

[kelvin@schettino ~]$ sudo chkconfig postgresql on [kelvin@schettino ~]$ sudo service postgresql start

Configure Postgres – Set superuser password

[kelvin@schettino ~]$ su - [root@schettino ~]# su - postgres -bash-4.1$ psql

postgres=# \password postgres Enter new password: Enter it again: postgres=# \q

Configure Postgres – Activate password authentication

By default, the server uses ident as defined in the “PostgreSQL Client Authentication Configuration File”. If you open up pg_hba.conf you can see this default configuration:

TYPE DATABASE USER CIDR-ADDRESS METHOD

"local" is for Unix domain socket connections only

local all all ident

IPv4 local connections:

host all all 127.0.0.1/32 ident

IPv6 local connections:

host all all ::1/128 ident

Ident is a mapping of local system users (see /etc/passwd for list of system users) to Postgres users. I have never found this authentication method useful for any of the web development work that I have done. I always change it to “md5″ which allows you to create arbitrary users and passwords. Let’s change the server’s client configuration file (I assume you are still using the postgres user shell):

-bash-4.1$ whoami postgres -bash-4.1$ vim /var/lib/pgsql/data/pg_hba.conf

Change the “ident” methods to “md5″ methods at the bottom of the pg_hba.conf file:

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

If you don't want to open Postgres to the Internet

don't enable this line

host all all 0.0.0.0/0 md5

By default, Postgres binds only to localhost and you will need to explicitly tell it to bind to your machine’s IP address. The setting is in postgres.conf. If you don’t need remote access you can skip this.

-bash-4.1$ vim /var/lib/pgsql/data/postgresql.conf

Change the listen_addresses setting to an asterisk to listen to all available IP addresses:

- Connection Settings -

listen_addresses = '' #listen_addresses = 'localhost' # what IP address(es) to listen on; # comma-separated list of addresses; # defaults to 'localhost', '' = all # (change requires restart)

Restart your postgres server (exit postgres user into the root shell): -bash-4.1$ exit [root@schettino ~]# service postgresql restart

Open Firewall

If you want remote access to the server on Postgres port 5432 you will have to open a port on the firewall. If you still are the root user, type the following:

[root@schettino ~]# whoami root [root@schettino ~]# vim /etc/sysconfig/iptables

You can just copy the SSH port rule in iptables and modify the port number from 22 to 5432.

Add the following rule just below the SSH port rule and above the rejection rule for the INPUT chain: 10

-A INPUT -m state --state NEW -m tcp -p tcp --dport 5432 -j ACCEPT

Reload the rules:

[root@schettino ~]# service iptables restart [root@schettino ~]# exit

Create a new Postgres user by using the createuser wrapper (the P switch allows you to set a password for your new user):

[kelvin@schettino ~]$ su - [root@schettino ~]# su - postgres -bash-4.1$ createuser -P francesco

Make a new database named “winnings” and change the owner to “francesco”: -bash-4.1$ createdb -O francesco winnings