presto-main/src/main/java/io/prestosql/operator/MultiChannelGroupByHash.java/MultiChannelGroupByHash/getEstimatedSize
class MultiChannelGroupByHash:    @Override
    public long getEstimatedSize()
    {
        return INSTANCE_SIZE +
                (sizeOf(channelBuilders.get(0).elements()) * channelBuilders.size()) +
                completedPagesMemorySize +
                currentPageBuilder.getRetainedSizeInBytes() +
                sizeOf(groupAddressByHash) +
                sizeOf(groupIdsByHash) +
                groupAddressByGroupId.sizeOf() +
                sizeOf(rawHashByHashPosition) +
                preallocatedMemoryInBytes;
    }