private void writeKVStateData() throws IOException, InterruptedException {
byte[] previousKey = null;
byte[] previousValue = null;
List<Tuple2<RocksIterator, Integer>> kvStateIteratorsHandover = this.kvStateIterators;
this.kvStateIterators = null;
// Here we transfer ownership of RocksIterators to the RocksDBMergeIterator
try (RocksDBMergeIterator mergeIterator =
new RocksDBMergeIterator(kvStateIteratorsHandover, stateBackend.keyGroupPrefixBytes)) {
// preamble: setup with first key-group as our lookahead
if (mergeIterator.isValid()) {
// begin first key-group by recording the offset
keyGroupRangeOffsets.setKeyGroupOffset(mergeIterator.keyGroup(), outStream.getPos());
// write the k/v-state id as metadata
// TODO this could be aware of keyGroupPrefixBytes and write only one byte if possible
outputView.writeShort(mergeIterator.kvStateId());
previousKey = mergeIterator.key();
previousValue = mergeIterator.value();
mergeIterator.next();
}
// main loop: write k/v pairs ordered by (key-group, kv-state), thereby tracking key-group
// offsets.
while (mergeIterator.isValid()) {
assert (!hasMetaDataFollowsFlag(previousKey));
// set signal in first key byte that meta data will follow in the stream after this k/v
// pair
if (mergeIterator.isNewKeyGroup() || mergeIterator.isNewKeyValueState()) {
// be cooperative and check for interruption from time to time in the hot loop
checkInterrupted();
setMetaDataFollowsFlagInKey(previousKey);
}
writeKeyValuePair(previousKey, previousValue);
// write meta data if we have to
if (mergeIterator.isNewKeyGroup()) {
// TODO this could be aware of keyGroupPrefixBytes and write only one byte if possible
outputView.writeShort(END_OF_KEY_GROUP_MARK);
// begin new key-group
keyGroupRangeOffsets.setKeyGroupOffset(mergeIterator.keyGroup(), outStream.getPos());
// write the kev-state
// TODO this could be aware of keyGroupPrefixBytes and write only one byte if possible
outputView.writeShort(mergeIterator.kvStateId());
} else if (mergeIterator.isNewKeyValueState()) {
// write the k/v-state
// TODO this could be aware of keyGroupPrefixBytes and write only one byte if possible
outputView.writeShort(mergeIterator.kvStateId());
}
// request next k/v pair
previousKey = mergeIterator.key();
previousValue = mergeIterator.value();
mergeIterator.next();
}
}
// epilogue: write last key-group
if (previousKey != null) {
assert (!hasMetaDataFollowsFlag(previousKey));
setMetaDataFollowsFlagInKey(previousKey);
writeKeyValuePair(previousKey, previousValue);
// TODO this could be aware of keyGroupPrefixBytes and write only one byte if possible
outputView.writeShort(END_OF_KEY_GROUP_MARK);
}
}
