Thread

1. Re: Bug #467: Can't insert a value of 0 (zero) into a Bytea

   Billy G. Allie <bill.allie@mug.org> — 2001-09-24T06:16:34Z

   pgsql-bugs@postgresql.org wrote:
   > Billy G. Allie (Bill.Allie@mug.org) reports a bug with a severity of 2
   > The lower the number the more severe it is.
   > 
   > Short Description
   > Can't insert a value of 0 (zero) into a Bytea type.
   > 
   > Long Description
   > It does not zeem possible to insert a value of zero (0) into a bytea type.  A
   > lso, using '\134' (the octal code for a backslash) causes byteain() to genera
   > te an error message.
   > 
   > As a side issue, how can one tell a backslash followed by 3 digits (four byte
   > s of data) from an encoded byte of data?  It seems to me that byteaout() shou
   > ld always output an octal escape sequence per byte, even if the character is 
   > printable.  That way the result is unambiguous in meaning (even if it is wast
   > eful of bytes).
   
   Further investigation provided the following information:
   
   1.  To insert a zero value the '\\000' sequence is required.
   
   2.  To insert a backslash, 4 backslashes are required (i.e. '\\\\')
   
   Therefore, to insert a backslash followed by the characters 1, 2, and 3 (four bytes of data), you would uses the sequence '\\\\123'.  On retrieval from the database, the sequence '\\123' would be returned.
   
   Can anyone confirm that this is correct.  If it is, then this bug report can be closed.
   
   Thanks.
   -- 
   ____       | Billy G. Allie    | Domain....: Bill.Allie@mug.org
   |  /|      | 7436 Hartwell     | MSN.......: B_G_Allie@email.msn.com
   |-/-|----- | Dearborn, MI 48126|
   |/  |LLIE  | (313) 582-1540    |
   
   
   

2. Re: Bug #467: Can't insert a value of 0 (zero) into a Bytea

   Joe Conway <joseph.conway@home.com> — 2001-09-25T04:05:39Z

   > > Short Description
   > > Can't insert a value of 0 (zero) into a Bytea type.
   > >
   > > Long Description
   > > It does not zeem possible to insert a value of zero (0) into a bytea
   type.  A
   > > lso, using '\134' (the octal code for a backslash) causes byteain() to
   genera
   > > te an error message.
   > >
   > > As a side issue, how can one tell a backslash followed by 3 digits (four
   byte
   > > s of data) from an encoded byte of data?  It seems to me that byteaout()
   shou
   > > ld always output an octal escape sequence per byte, even if the
   character is
   > > printable.  That way the result is unambiguous in meaning (even if it is
   wast
   > > eful of bytes).
   >
   > Further investigation provided the following information:
   >
   > 1.  To insert a zero value the '\\000' sequence is required.
   >
   > 2.  To insert a backslash, 4 backslashes are required (i.e. '\\\\')
   >
   > Therefore, to insert a backslash followed by the characters 1, 2, and 3
   (four
   > bytes of data), you would uses the sequence '\\\\123'.  On retrieval from
   the
   > database, the sequence '\\123' would be returned.
   >
   > Can anyone confirm that this is correct.  If it is, then this bug report
   can be closed.
   
   This was recently discussed on hackers (see
   http://fts.postgresql.org/db/mw/msg.html?mid=1032591), but the short answer
   is that you are correct (and that this is not a bug).
   
   [root@jec-linux /root]# psql -U postgres test
   Welcome to psql, the PostgreSQL interactive terminal.
   
   Type:  \copyright for distribution terms
          \h for help with SQL commands
          \? for help on internal slash commands
          \g or terminate with semicolon to execute query
          \q to quit
   
   test=# create table t1(f1 bytea);
   CREATE
   test=# insert into t1(f1) values('\\\\123');
   INSERT 1482289 1
   test=# select f1 from t1;
     f1
   -------
    \\123
   (1 row)
   
   test=# select octet_length(f1) from t1;
    octet_length
   --------------
               4
   (1 row)
   
   test=# insert into t1(f1) values('\\000');
   INSERT 1482290 1
   test=# select f1 from t1 where f1 = '\\000';
     f1
   ------
    \000
   (1 row)
   
   test=# select octet_length(f1) from t1 where f1 = '\\000';
    octet_length
   --------------
               1
   (1 row)
   
   
   HTH,
   
   -- Joe