RE: [Firebird-devel] Con||ca||te||na||tion again

[Claudio V. C. <cv...@us...>]

Ivan Prenosil wrote:
>
> Main reason why I do not use descriptors is that passing of blobs
> is broken -
> descriptor contains blob-id instead of pointer to blob-struct (hence
> it is not possible to write universal UDF, that could accept all
> types including blobs.).

Then you are saying that when you want descriptors, you don't want blob
descriptors. Obviously, the blob-struct is not the descriptor and lack the
flags of the descriptor. How do you tell the engine your returned blob is
null when using RETURNS PARAM? I had to use a trick: test if the blob handle
of the blob struct was set to a null pointer by the UDF.

I agree that the callback routines for reading/seeking/writing blobs should
check for the blob handle not being null before going ahead. What's trickier
is to ensure that the blob handle is valid... how about scanning all open
blobs known to the current txn?

C.