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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