/**
* Open an old, stored version of a map.
*
* @param version the version
* @return the read-only map
*/
@SuppressWarnings("unchecked")
<T extends BTreeMap<?, ?>> T openMapVersion(long version) {
BTreeChunk c = getChunkForVersion(version);
DataUtils.checkArgument(c != null, "Unknown version {0}", version);
BTreeMap<?, ?> m = map.openReadOnly();
m.setRootPos(c.rootPagePos, version);
return (T) m;
}
/**
* Revert to the beginning of the given version. All later changes (stored or not) are forgotten.
* All maps that were created later are closed. A rollback to a version before the last stored
* version is immediately persisted. Rollback to version 0 means all data is removed.
*
* @param version the version to revert to
*/
public synchronized void rollbackTo(long version) {
checkOpen();
if (version == 0) {
// special case: remove all data
map.close();
chunks.clear();
currentVersion = version;
return;
}
DataUtils.checkArgument(isKnownVersion(version), "Unknown version {0}", version);
map.internalRollbackTo(version);
boolean loadFromFile = false;
// find out which chunks to remove,
// and which is the newest chunk to keep
// (the chunk list can have gaps)
ArrayList<Integer> remove = new ArrayList<Integer>();
BTreeChunk keep = null;
for (BTreeChunk c : chunks.values()) {
if (c.version > version) {
remove.add(c.id);
} else if (keep == null || keep.id < c.id) {
keep = c;
}
}
if (remove.size() > 0) {
// remove the youngest first, so we don't create gaps
// (in case we remove many chunks)
Collections.sort(remove, Collections.reverseOrder());
map.removeUnusedOldVersions();
loadFromFile = true;
for (int id : remove) {
BTreeChunk c = chunks.remove(id);
c.fileStorage.close();
c.fileStorage.delete();
}
lastChunkId = keep.id;
setLastChunk(keep);
}
if (createVersion >= version) {
map.close();
} else {
if (loadFromFile) {
map.setRootPos(lastChunk.rootPagePos, lastChunk.version);
}
}
currentVersion = version;
}