Re: bytea question - Mailing list pgsql-general

From mjp@ornl.gov
Subject Re: bytea question
Date
Msg-id 20000815180850.C11670@grail.lsd.ornl.gov
Whole thread Raw
In response to Re: bytea question  (mikeo <mikeo@spectrumtelecorp.com>)
List pgsql-general
Oops! You have to write a function for it.  Here is a
sample quick C function:

typedef struct
{ int   len;
  char  data[1];
} string;

string *byteatostr(bytea *arg)
{
        char buf[1024];
        int ln,i;
        string *res;
        ln = VARSIZE(arg) - VARHDRSZ;
        memmove(buf, VARDATA(arg), ln);
        for(i=0; i < ln; i++)
         if( buf[i] < 32 ) buf[i]='?';

        res = (string *) palloc(VARHDRSZ + ln);
        memset(res, 0, VARHDRSZ + ln);
        res->len = VARHDRSZ + ln;
        memmove(res->data, buf, (int) ln);
        return res;
}

where all non-printable chars are replaced with '?'. Optionally,
the chars can be escaped (prefixed with '\') - adjusting ln as neccessry.


now you get:

# select byteatostr(col) from test2;

                         byteatostr
------------------------------------------------------------
 fk_uste_wu_id?us_states?web_users?UNSPECIFIED?wu_id?wu_id?
(1 rows)


'hope it works for you.

Morey Parang
ORNL

On Tue, Aug 15, 2000 at 05:23:38PM -0400, mikeo wrote:
> thanks anyway but that doesn't work.  i should've mentioned that i'd
> already tried that in SQL.  my apologies.
>
>
> tig4=# \d x
>           Table "x"
>  Attribute | Type  | Modifier
> -----------+-------+----------
>  tgargs    | bytea |
>
> tig4=# select substr(tgargs,1,5) from x;
> ERROR:  Function 'substr(bytea, int4, int4)' does not exist
>  Unable to identify a function that satisfies the given argument types
>  You may need to add explicit typecasts
>
> tig4=# select substr(tgargs::text,1,5) from x;
> ERROR:  Cannot cast type 'bytea' to 'text'
>
> and other things like varchar, etc.
>
> tig4=# select * from x;
>                                     tgargs
> ------------------------------------------------------------------------------
>  fk_uste_wu_id\000us_states\000web_users\000UNSPECIFIED\000wu_id\000wu_id\000
>  fk_uste_wu_id\000us_states\000web_users\000UNSPECIFIED\000wu_id\000wu_id\000
>  fk_uste_wu_id\000us_states\000web_users\000UNSPECIFIED\000wu_id\000wu_id\000
>
> what i'm looking to do here is to get the table names and column names out
> using sql.  i can do it in perl with a split command on '\' but was curious
> as to how to "SQL" split up a BYTEA type field.
>
> mikeo
>
>
> At 04:38 PM 8/15/00 -0400, mjp@ornl.gov wrote:
> >Try
> >
> >substr(text,int4) or
> >substr(text, int4, int4)
> >
> >For example,
> >
> >
> >% select substr('hi there',4,3);
> > substr
> >--------
> > the
> >(1 row)
> >
> >Morey Parang
> >ORNL
>

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