Reading BLOB in Native SQL from ABAP program

Question

Hello,
I'm trying to read content of a BLOB field from a table with Native SQL in ABAP like this:
DATA: l_bytes type xstring.
EXEC SQL.
  SELECT bytes INTO :l_bytes FROM tablename
ENDEXEC.
But when I'm using xstring it returns only 32768 bytes. When using type x length 65000 for l_bytes it returns 65000 bytes, but x is limited to 65535 bytes only. So why it returns only 32768 bytes in direct sql? For DB2 I found note 610342 where you need to add \lob to the statement, I tried with Oracle but doesn't work.
DATA: CLOB_VAR TYPE STRING.
DATA: BLOB_VAR TYPE XSTRING.
EXEC SQL.     
  SELECT FCLOB, FBLOB FROM ZZTAB        INTO :CLOB_VAR\lob, :BLOB_VAR\lob
ENDEXEC.
Regards
Markus

Answer 1

Hi Markus,
you have to read it in chunks (remember a blob could be up to 4 Gbyte!).
I assume you store the byte stream in the field (no bfile pointer to a file ).
Give you a pseudocode that you get the picture.
Would recommend that you read the Oracle manual (db Version?)
9i
http://download.oracle.com/docs/cd/B10501_01/appdev.920/a96612/d_lob2.htm#1008611
10g
http://download.oracle.com/docs/cd/B19306_01/appdev.102/b14258/d_lob.htm#ARPLS600
chunksize = 32768 .  " or use 65000 . This is the amount of the blob part you want to read
offset = 1.
*get the row of interest and retrieve blob's length
Exec sql.
select  dbms_lob.getlength(your_blob)  :blob_length from blob_table where my_primary_key = 1
end exec.
*calculate times to read from blob  until the end (well, leave the adjustment to you
* in case of an uneven  fraction)
ntimes = blob_length / chunksize .
Do ntimes
*loop and get the chunks into your variable:
* start reading from offset chunksize of bytes
exec sql.
select dbms_lob.substr(your_blob, :chunksize,:offset) into  :xblobvar  from blob_table
where my_primary_key = 1
endexec.
*don't know what you want to do with the blob chunk...
*process  :xblobvar
offset = chunksize * ntimes .
enddo.
bye
yk