cur = self.cursor()
+ # Find the id of the last snapshot to be created. This is used for
+ # measuring time in a way: we record this value in each segment we
+ # expire on this run, and then on a future run can tell if there have
+ # been intervening backups made.
+ cur.execute("select max(snapshotid) from snapshots")
+ last_snapshotid = cur.fetchone()[0]
+
# Get the list of old snapshots for this scheme. Delete all the old
# ones. Rules for what to keep:
# - Always keep the most recent snapshot.
cur.execute("""delete from segments where segmentid not in
(select segmentid from segments_used)""")
- # Finally, delete objects contained in non-existent segments. We can't
- # simply delete unused objects, since we use the set of unused objects
- # to determine the used/free ratio of segments.
+ # 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).
cur.execute("""delete from block_index
- where segmentid not in
- (select segmentid from segments)""")
+ where segmentid not in (select segmentid from segments)
+ or segmentid in (select segmentid from segments
+ where expire_time < ?)""",
+ (last_snapshotid,))
# Segment cleaning.
class SegmentInfo(Struct): pass
cur = self.cursor()
segments = []
cur.execute("""select segmentid, used, size, mtime,
- julianday('now') - mtime as age from segment_info""")
+ julianday('now') - mtime as age from segment_info
+ where expire_time is null""")
for row in cur:
info = self.SegmentInfo()
info.id = row[0]
raise TypeError("Invalid segment: %s, must be of type int or SegmentInfo, not %s" % (segment, type(segment)))
cur = self.cursor()
- cur.execute("update block_index set expired = 1 where segmentid = ?",
+ cur.execute("select max(snapshotid) from snapshots")
+ last_snapshotid = cur.fetchone()[0]
+ cur.execute("update segments set expire_time = ? where segmentid = ?",
+ (last_snapshotid, id))
+ cur.execute("update block_index set expired = 0 where segmentid = ?",
(id,))
def balance_expired_objects(self):
cutoffs.reverse()
for i in range(len(cutoffs)):
cur.execute("""update block_index set expired = ?
- where round(? - timestamp) > ?""",
+ where round(? - timestamp) > ?
+ and expired is not null""",
(i, now, cutoffs[i]))