Source Code for Module conduit.DeltaProvider

 1  """ 
 2  Shared API for comparing the previous state of a dp to the current  
 3  state. Returns only changes to core synch mechanism. 
 4   
 5  This class is a proxy for the TwoWay dataprovider. If the dataprovider 
 6  cannot implement get_changes() using backend dependant means this class  
 7  uses the mapping DB to implement get_changes() 
 8   
 9  This class will always be slower than if the backend implements the function 
10  iteself. 
11   
12  Copyright: John Stowers, 2006 
13  License: GPLv2 
14  """ 
15  import logging 
16  log = logging.getLogger("DeltaProvider") 
17   
18  import conduit 
19   
20 -class DeltaProvider: 
21 -    def __init__(self, dpw, otherdpw): 
22          self.me = dpw 
23          self.other = otherdpw 
24   
25          log.info("Delta: Source (%s) does not implement get_changes(). Proxying..." % self.me.get_UID()) 
26   
27 -    def get_changes(self): 
28          """ 
29          @returns: added, modified, deleted 
30          """ 
31          allItems = [] 
32          for i in self.me.module.get_all(): 
33              #Make sure the are in unicode to assure a  
34              #good comparison with mapping UID's 
35              if type(i) != unicode: 
36                  i = unicode(i,errors='replace') 
37              allItems.append(i) 
38   
39          log.debug("Delta: Got %s items\n%s" % (len(allItems), allItems)) 
40   
41          #In order to detect deletions we need to fetch all the existing relationships. 
42          #we also get the rids because we need those to detect if something has changed 
43          rids = {} 
44          for m in conduit.GLOBALS.mappingDB.get_mappings_for_dataproviders(self.me.get_UID(), self.other.get_UID()): 
45              rids[ m.get_source_rid().get_UID() ] = m.get_source_rid() 
46          for m in conduit.GLOBALS.mappingDB.get_mappings_for_dataproviders(self.other.get_UID(), self.me.get_UID()): 
47              rids[ m.get_sink_rid().get_UID() ] = m.get_sink_rid() 
48   
49          log.debug("Delta: Expecting %s items" % len(rids)) 
50          for uid,rid in rids.items(): 
51              log.debug("%s) -- %s" % (uid,rid)) 
52   
53          #now classify all my items relative to the expected data from the previous 
54          #sync with the supplied other dataprovider. Copy (slice) the list because we 
55          #modify it in place 
56          modified = [] 
57          for i in allItems[:]: 
58              if i in rids: 
59                  data = self.me.module.get(i) 
60                  if data.get_rid() != rids[i]: 
61                      log.debug("Modified: Actual:%s v DB:%s" % (data.get_rid(), rids[i])) 
62                      modified.append(i) 
63                  del(rids[i]) 
64                  allItems.remove(i) 
65   
66          #now all that remains in rids is data which has been deleted, 
67          #and all that remains in allItems is new data 
68          return allItems, modified, rids.keys() 
69