modules
+--------------+ +-----+
|planet.Channel|-+-is--|cache|
+----------+---+ \ +-----+
\ \ +------+
\ +-have-+-|dbhash|
\ / +------+
+--------+
dbhash
Planet(http://www.planetplanet.org/) uses the hashdb module to cache the feeded data.
The dbhash module provides a function to open databases using the BSD db library. This module mirrors the interface of the other Python database modules that provide access to DBM-style databases. The bsddb module is required to use dbhash.
"""output the hashdb"""
import sys
import dbhash
db = dbhash.open(sys.argv[1], 'r')
print db.first()
for i in xrange(1, len(db)):
print db.next()
db.close()
The dbm library was a simple database engine, originally written by Ken Thompson and released by AT&T in 1979. The name is a three letter acronym for database manager, and can also refer to the family of database engines with APIs and features derived from the original dbm.
planet.Channel and cache modules
the module description is very clear and easy to know, so you can use help() to show the module description and read it.
database file
the database is key/value database * " keys" is the key of the root item.
the root item's value is the keys of the channel properties that is splited by blank space.
the key in that there is not blank space is the key of the news item.
the news item's value is the keys of the news properties that is splited by blank space.
the news property's key is the unit of the news item's key and the part of the news item's value.
the channel property item and the news property item the key of that includes the string " type" is provided the type of the news property's value.
For example: the RSS:
CodePongo: json Thu, 22 Aug 2013 18:16:02 +0200 <h1>cJSON source analysis</h1>
the database:
(' keys', 'lastbuilddate title')
('lastbuilddate type', 'string')
('lastbuilddate', 'Thu, 22 Aug 2013 18:16:02 +0200')
('title type', 'string')
('title', 'CodePongo: json')
('http://codepongo.com/blog/3uhyc1/ title type', 'string')
('http://codepongo.com/blog/3uhyc1/ title', 'cJSON source analysis
')
('http://codepongo.com/blog/3uhyc1/', 'title')
