Problem with bytea

Started by Daniel Carlssonalmost 23 years ago2 messagesgeneral
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#1Daniel Carlsson
daniel.carlsson@gimlisoft.se

Hi

When a fetch binary data from a bytea column the data gets messed up.

Se the attached code, postgresql returns 13744 bytes when it should be only 10000. After studing the output I saw that bytes representing common characters are fetched ok but bytes representing unusual characters such as special swedish characters are messed up. Is the binary data somewhere treated as character data? Could something else be the problem?

I use RedHat 8.0, Postgresql 7.3.2 and jdbc driver pg73jdbc3.jar released 26:th of may.

Code:

Connection c = DriverManager.getConnection(jdbc);
Statement s = c.createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_UPDATABLE);
ResultSet r;

byte b[] = new byte[10000];

for(int i=0;i<b.length;i++)
b[i] = (byte)(i%256);

/* Update bytea with 10000 bytes */
s.executeUpdate("update document set file_=null where documentid=12");
r = s.executeQuery("select file_,documentid from document where documentid=17");
r.next();
r.updateBytes(1,b);
r.updateRow();

/* Fetch the bytea value */
r = s.executeQuery("select file_,documentid from document where documentid=17");
r.next();
b = r.getBytes(1);

/* This outputs 13744 !?!? */
System.out.println("Length: " + b.length);

Med vänliga hälsningar

Daniel Carlsson
Gimlisoft AB
Email: daniel.carlsson@gimlisoft.se
Tel: 0709-744570, 031-189024

#2Joe Conway
mail@joeconway.com
In reply to: Daniel Carlsson (#1)
Re: Problem with bytea

Daniel Carlsson wrote:

When a fetch binary data from a bytea column the data gets messed up.

Se the attached code, postgresql returns 13744 bytes when it should
be only 10000. After studing the output I saw that bytes representing
common characters are fetched ok but bytes representing unusual
characters such as special swedish characters are messed up. Is the
binary data somewhere treated as character data?

Yes, for output all "non-printable" characters are octal escaped. See:
http://www.us.postgresql.org/postgresql-7.3.3/datatype-binary.html

Joe