FileContentEntry
    hash              FileContentReference
    ix                Word64 
    chunkHash         FileContentChunkId
    UniqueFileContentEntry hash ix
    deriving Generic

FileContentChunk
    hash              FileContentChunkReference
    content           ByteString
    contentBased      Bool default=false -- For Migration
    Primary           hash
    deriving Generic

FileContentChunkUnreferenced
    hash              FileContentChunkId
    since             UTCTime
    UniqueFileContentChunkUnreferenced hash
    deriving Generic

SessionFile
    content         FileContentReference Maybe
    touched         UTCTime
    deriving Generic

FileLock
    content         FileContentReference
    instance        InstanceId
    time            UTCTime
    deriving Generic

FileChunkLock
    hash            FileContentChunkReference
    instance        InstanceId
    time            UTCTime
    deriving Generic