Re: Testing castability of text to numeric

>
> I thought that I would point out that an answer that answers my
> original query (how to test for castability without throwing
exception)
> was posted to the pgsql-general list on Sunday, by Joe Conway.  He has

> an "str_validate" set of functions which he makes available at
> joeconway.com.  Thanks to Joe.
>
And I thought it's useful to point out that these
Limitations
 Currently the only supported data types are:   - date   - timestamp   - interval

can easily be expanded for integer and float types using
the C code provided in ./src/backend/utils/adt/numutils.c

e.g. to test for integers

...
#include "postgres.h"

#include <errno.h> /* get declaration of errno */

#include "fmgr.h"
...switch (typeid){ case INT4OID:  {   long  l = 0;   char    *badp = NULL;
   errno = 0;
   /*    * Some versions of strtol treat the empty string as an error, but    * some seem not to.  Make an explicit
testto be sure we catch it.    */
 
   if (str == (char *) NULL)    PG_RETURN_BOOL(false);   else if (*str == 0)    PG_RETURN_BOOL(false);   else    l =
strtol(str,&badp, 10);
 
   /*    * strtol() normally only sets ERANGE. On some systems it also may    * set EINVAL, which simply means it
couldn'tparse the input
 
string.    * This is handled by the second "if" consistent across platforms.    */   if (errno && errno != EINVAL)
PG_RETURN_BOOL(false);  if (badp && *badp && *badp != 0)    PG_RETURN_BOOL(false);
 
   /* must be OK */   PG_RETURN_BOOL(true);  }  break;
 case DATEOID:
...

Regards, Christoph

PS I am not subscribed to the pgsql-general list, so may be someone who
is
would like to forward this. Thanks. And thanks to Joe for inspiration.