Thread: inet versus text for ip addresses

The PostgreSQL inet datatype stores an holds an IP host address, and 
optionally the identity of the subnet it is in, all in one field.  
This requires 12 bytes.   

Using my "random" data of approximately 8000 IP addresses collected 
during previous polls, I've found the average length of an IP address 
is 13.1 bytes.    An integer requires 4 bytes.

First question: Why not store an option to store just an IP address?  
That should require less than the 12 bytes for inet.

On to the real question:

The existing tables are:

create table recount_ips
(   ipid        serial                not null,   ipaddress   inet                  not null,   primary key (ipid)
);

create unique index recount_ips_ip_address on recount_ips 
(ipaddress);

create table recount_iptopolls
(   pollid      integer               not null,   ipid        integer               not null,   primary key (pollid,
ipid)
);

alter table recount_iptopolls   add foreign key  (pollid)      references recount_polls (pollid) on update restrict on
delete
 
restrict;

alter table recount_iptopolls   add foreign key  (ipid)      references recount_ips (ipid) on update restrict on delete

restrict;



I think a better solution is one table:

create table recount_iptopolls
(   pollid      integer               not null,   ipaddress   inet                  not null,   primary key (pollid,
ipaddress)
);

alter table recount_iptopolls   add foreign key  (pollid)      references recount_polls (pollid) on update restrict on
delete
 
restrict;

It removes a table and the associated primary key, and removed a 
foreign key from the modified recount_iptopolls table.

Comments?
-- 
Dan Langille : http://www.langille.org/

Dan Langille wrote:
> The PostgreSQL inet datatype stores an holds an IP host address, and 
> optionally the identity of the subnet it is in, all in one field.  
> This requires 12 bytes.   
> 
> Using my "random" data of approximately 8000 IP addresses collected 
> during previous polls, I've found the average length of an IP address 
> is 13.1 bytes.    An integer requires 4 bytes.
> 
> First question: Why not store an option to store just an IP address?  
> That should require less than the 12 bytes for inet.

We store inet and cidr in similar structures, and they are of variable
length (4 byte overhead):
/* *  This is the internal storage format for IP addresses *  (both INET and CIDR datatypes): */typedef struct{
unsignedchar family;    unsigned char bits;    unsigned char type;    union    {        unsigned int ipv4_addr; /*
networkbyte order */        /* add IPV6 address type here */    }           addr;} inet_struct;/* * Both INET and CIDR
addressesare represented within Postgres as varlena * objects, ie, there is a varlena header (basically a length word)
infront * of the struct type depicted above. * * Although these types are variable-length, the maximum length * is
prettyshort, so we make no provision for TOASTing them. */typedef struct varlena inet;
 

In 7.4, we support IPv6, so they will be even larger.


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