At 02:17 PM 27/05/2004 +0200, you wrote:

> > SELECT FILTER(MyBlobColumn, -2, 1)
> > etc...
>
>2 details :
>
>1) It would be nice to be consistent with SUBSTRING syntax
>2) Blobs already have a sub_type defined a declaration time. So "-2" is not
>required.
>
>So it could be :
>
>SELECT FILTER(MyBlob TO SUB_TYPE 1) FROM MyTable...

Actually, you do need the sub_types of both the "source" and the "target"
blobs. Every Blob filter operation must operate on a pair of subtypes...

The engine doesn't do any checking to make sure that MyBlob (in your
example) can validly be processed by your blobfilter code (convert a zip
file to a jpeg?). It doesn't know any of the rules, so it's up to the
programmer to ensure that the engine doesn't throw the wrong sort of
parameter at the blob filter code. External function code that chokes does
veeeerrry horrible things to the server.

/heLen

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