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PostgreSQL的类型支持比较强大, 除了主流的文本, 日期, 时间, 数字, 还支持JSON, 货币, 网络, 几何, 枚举, 数组, 范围, XML, 布尔, 全文检索, 比特, 复合等数据类型.
MySQL的类型支持比较薄弱, MySQL里面没有专门的网络数据类型, 如果要存储网络信息, 一般的做法是转换成INT类型来处理.
PostgreSQL当然没有必要这么做, 因为已经支持inet和cidr类型了, 操作极为方便. 开发人员使用PostgreSQL会比较愉快.
例如
| >> |
contains |
inet '192.168.1/24' >> inet '192.168.1.5' |
digoal=# select inet '192.168.1/24' >> inet '192.168.2.1'
digoal-# ;
?column?
----------
f
(1 row)
digoal=# select inet '192.168.1/24' >> inet '192.168.2.1';
?column?
----------
f
(1 row)
digoal=# select inet '192.168.1/24' >> inet '192.168.1.100';
?column?
----------
t
(1 row)
digoal=# select inet '192.168.1.0/24' >> inet '192.168.1.100';
?column?
----------
t
(1 row)
digoal=# select inet '192.168.1.128/25' >> inet '192.168.1.100';
?column?
----------
f
(1 row)
digoal=# select inet '192.168.1.128/25' >> inet '192.168.1.129';
?column?
----------
t
(1 row)
本文模拟在没有INET或者cidr类型的时候的使用方法.
那么我这里要说的是如果你是从mysql转到pg的, 并且前期不想改代码的话, 那么就需要写一些和MySQL兼容的函数.
例如MySQL里面的inet_aton , inet_ntoa.
-
INET_ATON(expr)
Given the dotted-quad representation of an IPv4 network address as a string, returns an integer that represents the numeric value of the address in network byte order (big endian). INET_ATON() returns NULL if it does not understand its argument.
mysql> SELECT INET_ATON('10.0.5.9');
-> 167773449
For this example, the return value is calculated as 10×2563 + 0×2562 + 5×256 + 9.
INET_ATON() may or may not return a non-NULL result for short-form IP addresses (such as '127.1' as a representation of '127.0.0.1'). Because of this, INET_ATON()a should not be used for such addresses.
Note
To store values generated by INET_ATON(), use an INT UNSIGNED column rather than INT, which is signed. If you use a signed column, values corresponding to IP addresses for which the first octet is greater than 127 cannot be stored correctly. See Section 11.2.6, “Out-of-Range and Overflow Handling”.
-
INET_NTOA(expr)
Given a numeric IPv4 network address in network byte order, returns the dotted-quad string representation of the address as a nonbinary string in the connection character set. INET_NTOA() returns NULL if it does not understand its argument.
mysql> SELECT INET_NTOA(167773449);
-> '10.0.5.9'
在PostgreSQL可以通过如下自定义函数来实现 :
create or replace function inet_aton(ip text) returns int8 as $$
declare
v int;
res int8 := 0;
i int := 3;
begin
foreach v in array string_to_array(ip, '.') loop
res := res+v*(256^i);
i := i-1;
end loop;
return res;
end;
$$ language plpgsql;
create or replace function inet_ntoa(ip int8) returns text as $$
declare
res text := '';
begin
res := res || ((ip >> 24) & (2^8-1)::int);
res := res || '.' || ((ip >> 16) & (2^8-1)::int);
res := res || '.' || ((ip >> 8) & (2^8-1)::int);
res := res || '.' || (ip & (2^8-1)::int);
return res;
end;
$$ language plpgsql;
测试 :
digoal=# select inet_aton('192.168.9.100');
inet_aton
------------
3232237924
(1 row)
digoal=# select inet_ntoa(3232237924);
inet_ntoa
---------------
192.168.9.100
(1 row)
在MySQL中假如存储了IP和子网掩码的值, 我们可以通过如下方法来判断IP是否在这个子网中.
1. 从IP和子网掩码运算得到net和broadcast, 然后转换成INT8.
2. 把要匹配的IP转换成INT8, 与第一步得到的值进行比较
例如 :
192.168.9.0/24
192.168.9.128/25
192.168.9.0/25
192.168.0.0/16
转换成net和broadcast
192.168.9.0, 192.168.9.255
192.168.9.128, 192.168.9.255
192.168.9.0, 192.168.9.127
192.168.0.0, 192.168.255.255
net的转换方法如下 :
digoal=# select substring('192.168.9.0/24','(.*)/\d*');
substring
-------------
192.168.9.0
(1 row)
broadcast的转换方法如下 :
digoal=# select inet_ntoa((inet_aton(substring('192.168.9.0/24','(.*)/\d*')) + 2^(32-substring('192.168.9.0/24','.*/(\d*)')::int) -1)::int8);
inet_ntoa
---------------
192.168.9.255
(1 row)
转换成数字就可以做比较了.
digoal=# create table t1 (ip text, inet text);
CREATE TABLE
digoal=# insert into t1 values ('192.168.1.1','192.168.1.128/25');
INSERT 0 1
digoal=# insert into t1 values ('192.168.1.10','192.168.1.0/25');
INSERT 0 1
digoal=# insert into t1 values ('192.168.1.129','192.168.1.128/25');
INSERT 0 1
digoal=# select inet, substring(inet,'(.*)/\d*') as net, inet_ntoa((inet_aton(substring(inet,'(.*)/\d*')) + 2^(32-substring(inet,'.*/(\d*)')::int) -1)::int8) as broadcast from t1;
inet | net | broadcast
------------------+---------------+---------------
192.168.1.128/25 | 192.168.1.128 | 192.168.1.255
192.168.1.0/25 | 192.168.1.0 | 192.168.1.127
192.168.1.128/25 | 192.168.1.128 | 192.168.1.255
(3 rows)
查看IP是否落在IPNET范围内.
digoal=# select * from (select ip, inet, substring(inet,'(.*)/\d*') as net, inet_ntoa((inet_aton(substring(inet,'(.*)/\d*')) + 2^(32-substring(inet,'.*/(\d*)')::int) -1)::int8) as broadcast from t1) t where inet_aton(ip) > inet_aton(net) and inet_aton(ip) < inet_aton(broadcast);
ip | inet | net | broadcast
---------------+------------------+---------------+---------------
192.168.1.10 | 192.168.1.0/25 | 192.168.1.0 | 192.168.1.127
192.168.1.129 | 192.168.1.128/25 | 192.168.1.128 | 192.168.1.255
(2 rows)
[参考]
1. http://dev.mysql.com/doc/refman/5.5/en/miscellaneous-functions.html#function_inet-aton
2. http://doxygen.postgresql.org/inet__aton_8c_source.html#l00054
3. http://www.postgresql.org/docs/9.3/static/datatype-net-types.html
4. http://www.postgresql.org/docs/9.3/static/functions-net.html
5. http://doxygen.postgresql.org/inet__aton_8c_source.html#l00054
