Improve tracking of segments and segment utilization.

[cumulus.git] / python / cumulus / __init__.py

diff --git a/python/cumulus/__init__.py b/python/cumulus/__init__.py
index 51755c7..a40c58d 100644 (file)
--- a/python/cumulus/__init__.py
+++ b/python/cumulus/__init__.py
@@ -532,7 +532,26 @@ class LocalDatabase:
         schemes.sort()
         return schemes
 
         schemes.sort()
         return schemes
 

-    def garbage_collect(self, scheme, intent=1.0):
+    def list_snapshots(self, scheme):
+        """Return a list of snapshots for the given scheme."""
+        cur = self.cursor()
+        cur.execute("select name from snapshots")
+        snapshots = [row[0] for row in cur.fetchall()]
+        snapshots.sort()
+        return snapshots
+
+    def delete_snapshot(self, scheme, name):
+        """Remove the specified snapshot from the database.
+
+        Warning: This does not garbage collect all dependent data in the
+        database, so it must be followed by a call to garbage_collect() to make
+        the database consistent.
+        """
+        cur = self.cursor()
+        cur.execute("delete from snapshots where scheme = ? and name = ?",
+                    (scheme, name))
+
+    def prune_old_snapshots(self, scheme, intent=1.0):

         """Delete entries from old snapshots from the database.
 
         Only snapshots with the specified scheme name will be deleted.  If
         """Delete entries from old snapshots from the database.
 
         Only snapshots with the specified scheme name will be deleted.  If


@@ -579,6 +598,16 @@ class LocalDatabase:
             first = False
             max_intent = max(max_intent, snap_intent)
 
             first = False
             max_intent = max(max_intent, snap_intent)
 

+        self.garbage_collect()
+
+    def garbage_collect(self):
+        """Garbage-collect unreachable segment and object data.
+
+        Remove all segments and checksums which is not reachable from the
+        current set of snapshots stored in the local database.
+        """
+        cur = self.cursor()
+

         # Delete entries in the segments_used table which are for non-existent
         # snapshots.
         cur.execute("""delete from segments_used
         # Delete entries in the segments_used table which are for non-existent
         # snapshots.
         cur.execute("""delete from segments_used


@@ -590,16 +619,10 @@ class LocalDatabase:
         cur.execute("""delete from segments where segmentid not in
                            (select segmentid from segments_used)""")
 
         cur.execute("""delete from segments where segmentid not in
                            (select segmentid from segments_used)""")
 

-        # Delete unused objects in the block_index table.  By "unused", we mean
-        # any object which was stored in a segment which has been deleted, and
-        # any object in a segment which was marked for cleaning and has had
-        # cleaning performed already (the expired time is less than the current
-        # largest snapshot id).
+        # Delete dangling objects in the block_index table.

         cur.execute("""delete from block_index
         cur.execute("""delete from block_index

-                       where segmentid not in (select segmentid from segments)
-                          or segmentid in (select segmentid from segments
-                                           where expire_time < ?)""",
-                    (last_snapshotid,))
+                       where segmentid not in
+                           (select segmentid from segments)""")

 
         # Remove sub-block signatures for deleted objects.
         cur.execute("""delete from subblock_signatures
 
         # Remove sub-block signatures for deleted objects.
         cur.execute("""delete from subblock_signatures