6

I am trying to export an image file from a PostgreSQL database.The users_data_circulation table has a photo (bytea) column.

My command:

copy (select encode(photo,'hex') from users_data_circulation limit 1)
    TO '/tmp/imagetest.hext';

In operating system:

$> xxd -p -r /tmp/imagetest.hex > /tmp/imagetest.jpg
$> file /tmp/imagetest.jpg
/tmp/imagetest.jpg: ASCII TEXT

I can't open the jpg file. How can I convert this file to jpg?

devinim@devinimpostgresql:~$ hexdump -C /tmp/image.hex | more
00000000  5c 5c 33 37 37 5c 5c 33  33 30 5c 5c 33 37 37 5c  |\\377\\330\\377\|
00000010  5c 33 34 30 5c 5c 30 30  30 10 4a 46 49 46 5c 5c  |\340\\000.JFIF\\|
00000020  30 30 30 01 02 5c 5c 30  30 30 5c 5c 30 30 30 01  |000..\\000\\000.|
00000030  5c 5c 30 30 30 01 5c 5c  30 30 30 5c 5c 30 30 30  |\\000.\\000\\000|
00000040  5c 5c 33 37 37 5c 5c 33  34 31 5c 5c 30 30 30 5c  |\\377\\341\\000\|
00000050  76 50 49 43 5c 5c 30 30  30 02 5c 6e 5c 6e 01 5c  |vPIC\\000.\n\n.\|
00000060  5c 30 30 30 5c 5c 33 37  37 5c 5c 33 37 36 5c 5c  |\000\\377\\376\\|
00000070  30 30 30 21 50 69 63 74  75 72 65 20 45 6c 65 6d  |000!Picture Elem|
00000080  65 6e 74 73 2c 20 49 6e  63 2e 20 49 53 45 2f 53  |ents, Inc. ISE/S|
... continues like that
1
  • 2
    The content looks like it was generated by encode(photo,'escape') rather than encode(photo,'hex'). Oct 3 '16 at 12:54
4

It's a horrible idea to store jpegs in the database.

That said, if you want to get it out of the database, you can use psql. This gets it out as hex.

psql -t -A -o "/tmp/imagetest.jpg" -c \
  "SELECT photo FROM users_data_circulation LIMIT 1";

You may also want to check out the large object.

1
-1
    DO $$ 
DECLARE   
   l_lob_id OID;
   r record; BEGIN

  for r in
    select data, filename from bytea_table

   LOOP
    l_lob_id:=lo_from_bytea(0,r.data);
    PERFORM lo_export(l_lob_id,'/home/...'||r.filename);
    PERFORM lo_unlink(l_lob_id);   
    END LOOP;

END; $$
0

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