Examples with Iterators com.google.common.collect.Iterators used on opensource projects

Example 1 with Iterators

use of com.google.common.collect.Iterators in project CorfuDB by CorfuDB.

the class CheckpointWriter method appendObjectState.

/** Append zero or more CONTINUATION records to this
     *  object's stream.  Each will contain a fraction of
     *  the state of the object that we're checkpointing
     *  (up to batchSize items at a time).
     *
     *  Corfu client transaction management, if desired, is the
     *  caller's responsibility.
     *
     *  The Iterators class appears to preserve the laziness
     *  of Stream processing; we don't wish to use more
     *  memory than strictly necessary to generate the
     *  checkpoint.  NOTE: It would be even more useful if
     *  the map had a lazy iterator: the eagerness of
     *  map.keySet().stream() is not ideal, but at least
     *  it should be much smaller than the entire map.
     *
     *  NOTE: The postAppendFunc lambda is executed in the
     *  current thread context, i.e., inside of a Corfu
     *  transaction, and that transaction will be *aborted*
     *  at the end of this function.  Any Corfu data
     *  modifying ops will be undone by the TXAbort().
     *
     * @return Stream of global log addresses of the
     * CONTINUATION records written.
     */
public List<Long> appendObjectState() {
    ImmutableMap<CheckpointEntry.CheckpointDictKey, String> mdKV = ImmutableMap.copyOf(this.mdKV);
    List<Long> continuationAddresses = new ArrayList<>();
    Iterators.partition(map.keySet().stream().map(k -> {
        return new SMREntry("put", new Object[] { keyMutator.apply(k), valueMutator.apply(map.get(k)) }, serializer);
    }).iterator(), batchSize).forEachRemaining(entries -> {
        MultiSMREntry smrEntries = new MultiSMREntry();
        for (int i = 0; i < ((List) entries).size(); i++) {
            smrEntries.addTo((SMREntry) ((List) entries).get(i));
        }
        CheckpointEntry cp = new CheckpointEntry(CheckpointEntry.CheckpointEntryType.CONTINUATION, author, checkpointID, mdKV, smrEntries);
        long pos = sv.append(Collections.singleton(streamID), cp, null);
        postAppendFunc.accept(cp, pos);
        continuationAddresses.add(pos);
        numEntries++;
        numBytes += cp.getSmrEntriesBytes();
    });
    return continuationAddresses;
}