frappe/py/webnotes/utils/cache.py

# Copyright (c) 2012 Web Notes Technologies Pvt Ltd (http://erpnext.com)
# 
# MIT License (MIT)
# 
# Permission is hereby granted, free of charge, to any person obtaining a 
# copy of this software and associated documentation files (the "Software"), 
# to deal in the Software without restriction, including without limitation 
# the rights to use, copy, modify, merge, publish, distribute, sublicense, 
# and/or sell copies of the Software, and to permit persons to whom the 
# Software is furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in 
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
# INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A 
# PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT 
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF 
# CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE 
# OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
# 

from __future__ import unicode_literals
"""
Simple Caching:

Stores key-value pairs in database and enables simple caching

CacheItem(key).get() returns the cached value if not expired (else returns null)
CacheItem(key).set(interval = 60000) sets a value to cache, expiring after x seconds
CahceItem(key).clear() clears an old value
setup() sets up cache
"""

import webnotes

def clear():
	"""clear doctype cache"""
	try:
		webnotes.conn.sql("""delete from __CacheItem""")
	except Exception, e:
		if e.args[0]!=1146: raise e

class CacheItem:
	def __init__(self, key):
		"""create a new cache"""
		self.key = key
	
	def get(self):
		"""get value"""
		try:
			return webnotes.conn.sql("""select `value` from __CacheItem where 
				`key`=%s and ifnull(expires_on, '2100-01-01') > NOW()""", self.key)[0][0]
		except Exception:
			return None
	
	def set(self, value, interval=None):
		"""set a new value, with interval"""
		self.clear()
		if interval:
			webnotes.conn.sql("""insert into 
					__CacheItem (`key`, `value`, expires_on) 
				values (%s, %s, addtime(now(), sec_to_time(%s)))
				""", (self.key, str(value), interval))
		else:
			webnotes.conn.sql("""insert into 
					__CacheItem (`key`, `value`) 
				values (%s, %s)
				""", (self.key, str(value)))
			
	
	def clear(self):
		"""clear the item"""
		try:
			webnotes.conn.sql("delete from __CacheItem where `key`=%s", self.key)
		except Exception, e:
			if e.args[0]!=1146: raise e