Обсуждение: Problem with do_quote_ident()

I see in quote.c::do_quote_ident():
*cp2++ = '"';while (len-- > 0){    if (*cp1 == '"')        *cp2++ = '"';    if (*cp1 == '\\')        *cp2++ = '\\';
*cp2++= *cp1++;}*cp2++ = '"';
 

I am confused by the backslash handling. In my tests, a backslash in a
double-quoted string does not require two backslashes:test=> create user "a\d";CREATE USERtest=> select usename,
length(usename)from pg_user; usename  | length ----------+-------- a\d      |      3
 

This is because a double-quote in a double-quoted string is entered as
"", not \".

Is it adding another backslash because it assumes the result will appear
in another quoted string?

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
853-3000+  If your life is a hard drive,     |  830 Blythe Avenue +  Christ can be your backup.        |  Drexel Hill,
Pennsylvania19026
 

Bruce Momjian wrote:
> I see in quote.c::do_quote_ident():
>
>    *cp2++ = '"';
>    while (len-- > 0)
>    {
>         if (*cp1 == '"')
>              *cp2++ = '"';
>         if (*cp1 == '\\')
>              *cp2++ = '\\';
>         *cp2++ = *cp1++;
>    }
>    *cp2++ = '"';
>
> I am confused by the backslash handling. In my tests, a backslash in a
> double-quoted string does not require two backslashes:
>
>    test=> create user "a\d";
>    CREATE USER
>    test=> select usename, length(usename) from pg_user;
>     usename  | length
>    ----------+--------
>     a\d      |      3
>
> This is because a double-quote in a double-quoted string is entered as
> "", not \".
>
> Is it adding another backslash because it assumes the result will appear
> in another quoted string?
   I  would  say  it is adding another backslash because it is a   bug.  If you use quote_ident()  in  a  plpgsql
procedure to   build  querystrings  for  EXECUTE  (and you should do it that   way),  then  it'll  no  handle
identifiers  that   contain   backslashes correctly.
 


Jan

--

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