Major Description
Now, org.apache.derby.impl.jdbc.EmbedBlob#length() method read out whole BinaryToRawStream to know exact length.
On the other hand, BinaryToRawStream have some commented-out inplementation of having information for length.
I think the information of lengh in BinaryToRawStream should be restored to be used in .org.apache.derby.impl.jdbc.EmbedBlob#length(), because read out whole stream can be expensive processing when streamed information was large.
There exists a subject that reliability of lengh information in BinaryToRawStream is unknown.