sqliteAndPrevayler.py

from pv.core import PSys, Log
from pysqlite2 import dbapi2 as sqlite
import os, time


class Root:
    def __init__(self):
        self.attributes = {}
        self.dbConn = sqlite.connect(":memory:")        
        self.createInitialSchema()

    def createInitialSchema(self):
        "Alternatively it can also be a separate transaction"
        cur = self.dbConn.cursor()
        cur.execute("create table props(name string, value string);")

    def __getstate__(self, value):        
        value = {"attributes": self.attributes,
                 "dbState" : self.dbConn.iterdump()}
        return value

    def __setstate__(self, value):
        self.attributes = value["attributes"]        
        self.dbConn = sqlite.connect(":memory:")
        for sqlCmd in value["dbState"]:
            self.dbConn.cursor().execute(sqlCmd) 


class DbTx:
    def __init__(self, name, val):
        self.name = name
        self.val = val    

    def __call__(self, root): 
        cur = root.dbConn.cursor()
        cur.execute("insert into props (name, value) values (?, ?)", [self.name, self.val])
        root.attributes["dirty"] = True


def someFn(root):
    "Simple operation"    
    root.attributes["dirty"] = False


def showProps(root):
    cur = root.dbConn.cursor()
    return cur.execute("select * from props").fetchall()


if __name__ == "__main__":
    dataDir = "./data"
    if not os.path.isdir(dataDir):
        os.makedirs(dataDir)
    psys = PSys(Log(dataDir), lambda : Root())
    psys.exe(DbTx("level", time.time()))
    psys.exe(someFn)
    print "props", showProps(psys.root)
    print "attributes", psys.root.attributes
    psys.log.close()