BlockCursor probeJoinCursor = probeJoinBlock.cursor();
for (int position = 0; position < page.getPositionCount(); position++) {
checkState(probeJoinCursor.advanceNextPosition());
if (probeJoinCursor.isNull(0)) {
blockBuilder.appendNull();
}
else {
boolean contains = channelSet.contains(probeJoinCursor);
if (!contains && channelSet.containsNull()) {
blockBuilder.appendNull();