Re: unknownin/out patch (was [HACKERS] PQescapeBytea is - Mailing list pgsql-patches

Joe Conway wrote:
> Tatsuo Ishii wrote:
>  >>> Tatsuo Ishii wrote:
>  >>>
>  >>>>
>  >>>> Try a multibyte encoding database. For example,
>  >>>>
>  >>>> $ createdb -E EUC_JP test $ psql -c 'SELECT
>  >>>> SUBSTRING('1234567890' FROM 3)' test substring ----------- 3456
>  >>>>
>
>  >>>> (1 row)
>  >>>>
>  >>>> Apparently this is wrong. -- Tatsuo Ishii
>  >>>
>  >>> This problem exists in CVS tip *without* the unknownin/out
>  >>> patch:
>  >>
>  >> Sure. That has been broken for a while.
>  >
>  >
>  > I guess this actually happened in 1.79 of varlena.c:
>  >
> Yes, I was just looking at that also. It doesn't consider the case of n
> = -1 for MB. See the lines:
>
> #ifdef MULTIBYTE
>    eml = pg_database_encoding_max_length ();
>
>    if (eml > 1)
>    {
>       sm = 0;
>       sn = (m + n) * eml + 3;
>    }
> #endif
>
> When n = -1 this does the wrong thing. And also a few lines later:
>
> #ifdef MULTIBYTE
>    len = pg_mbstrlen_with_len (VARDATA (string), sn - 3);
>
> I think both places need to test for n = -1. Do you agree?
>
>
> Joe
>

The attached patch should fix the bug reported by Tatsuo.

# psql -U postgres testjp
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

testjp=# SELECT SUBSTRING('1234567890' FROM 3);
  substring
------------
  34567890
(1 row)

Joe
*** pgsql/src/backend/utils/adt/varlena.c    Sun Apr  7 11:44:54 2002
--- pgsql.orig/src/backend/utils/adt/varlena.c    Mon Apr  8 22:32:16 2002
***************
*** 413,419 ****
      if (eml > 1)
      {
          sm = 0;
!         sn = (m + n) * eml + 3; /* +3 to avoid mb characters overhanging slice end */
      }
  #endif

--- 373,382 ----
      if (eml > 1)
      {
          sm = 0;
!         if (n > -1)
!             sn = (m + n) * eml + 3; /* +3 to avoid mb characters overhanging slice end */
!         else
!             sn = n;        /* n < 0 is special-cased by heap_tuple_untoast_attr_slice */
      }
  #endif

***************
*** 427,433 ****
      PG_RETURN_NULL();   /* notreached: suppress compiler warning */
  #endif
  #ifdef MULTIBYTE
!     len = pg_mbstrlen_with_len (VARDATA (string), sn - 3);

      if (m > len)
      {
--- 390,399 ----
      PG_RETURN_NULL();   /* notreached: suppress compiler warning */
  #endif
  #ifdef MULTIBYTE
!     if (n > -1)
!         len = pg_mbstrlen_with_len (VARDATA (string), sn - 3);
!     else    /* n < 0 is special-cased; need full string length */
!         len = pg_mbstrlen (VARDATA (string));

      if (m > len)
      {