To retrieve LOB locators as streams, specify the type of retrieved object as
in the query. For example:
(sql:select [image :input-stream] :from [mytable] :flatp t)
returns a list of streams.
For example, to print the name of all images that start with some "magic number", that is a sequence of 4 specific bytes (#xf5 #x12 #x4e #x23):
(let ((array (make-array 4 :element-type '(unsigned-byte 8))))
(sql:do-query ((name lob-stream)
[sql:select [name][image :input-stream]
(when (and (eq (read-sequence array lob-stream ) 4)
(eq (aref array 0) #xf5)
(eq (aref array 0) #x12)
(eq (aref array 0) #x4e)
(eq (aref array 0) #x23))
Closing the stream also frees the LOB object.
, it is important to call
before trying to commit the changes, because the stream is buffered.