Re: Collation rules and multi-lingual databases

Joe Conway wrote:
> What about something like this?

Oops! Forgot to restrore error handling. See below:

Joe

> 8<--------------------------------
> 
> #include <setjmp.h>
> #include <string.h>
> 
> #include "postgres.h"
> #include "fmgr.h"
> #include "tcop/tcopprot.h"
> #include "utils/builtins.h"
> 
> #define GET_STR(textp) \
>   DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(textp)))
> #define GET_BYTEA(str_) \
>   DatumGetTextP(DirectFunctionCall1(byteain, CStringGetDatum(str_)))
> #define MAX_BYTEA_LEN    0x3fffffff
> 
> /*
>  * pg_strxfrm - Function to convert string similar to the strxfrm C
>  * function using a specified locale.
>  */
> extern Datum pg_strxfrm(PG_FUNCTION_ARGS);
> PG_FUNCTION_INFO_V1(pg_strxfrm);
> 
> Datum
> pg_strxfrm(PG_FUNCTION_ARGS)
> {
>   char       *str = GET_STR(PG_GETARG_TEXT_P(0));
>   size_t      str_len = strlen(str);
>   char       *localestr = GET_STR(PG_GETARG_TEXT_P(1));
>   size_t      approx_trans_len = 4 + (str_len * 3);
>   char       *trans = (char *) palloc(approx_trans_len + 1);
>   size_t      actual_trans_len;
>   char       *oldlocale;
>   char       *newlocale;
>   sigjmp_buf  save_restart;
> 
>   if (approx_trans_len > MAX_BYTEA_LEN)
>     elog(ERROR, "source string too long to transform");
> 
>   oldlocale = setlocale(LC_COLLATE, NULL);
>   if (!oldlocale)
>     elog(ERROR, "setlocale failed to return a locale");
> 
>   /* catch elog while locale is set other than the default */
>   memcpy(&save_restart, &Warn_restart, sizeof(save_restart));
>   if (sigsetjmp(Warn_restart, 1) != 0)
>   {
>     memcpy(&Warn_restart, &save_restart, sizeof(Warn_restart));
>     newlocale = setlocale(LC_COLLATE, oldlocale);
>     if (!newlocale)
>       elog(PANIC, "setlocale failed to reset locale: %s", localestr);
>     siglongjmp(Warn_restart, 1);
>   }
> 
>   newlocale = setlocale(LC_COLLATE, localestr);
>   if (!newlocale)
>     elog(ERROR, "setlocale failed to set a locale: %s", localestr);
> 
>   actual_trans_len = strxfrm(trans, str, approx_trans_len + 1);
> 
>   /* if the buffer was not large enough, resize it and try again */
>   if (actual_trans_len >= approx_trans_len)
>   {
>     approx_trans_len = actual_trans_len + 1;
>     if (approx_trans_len > MAX_BYTEA_LEN)
>       elog(ERROR, "source string too long to transform");
> 
>     trans = (char *) repalloc(trans, approx_trans_len + 1);
>     actual_trans_len = strxfrm(trans, str, approx_trans_len + 1);
> 
>     /* if the buffer still not large enough, punt */
>     if (actual_trans_len >= approx_trans_len)
>       elog(ERROR, "strxfrm failed, buffer insufficient");
>   }
> 
>   newlocale = setlocale(LC_COLLATE, oldlocale);
>   if (!newlocale)
>     elog(PANIC, "setlocale failed to reset locale: %s", localestr);
  /* restore normal error handling */  memcpy(&Warn_restart, &save_restart, sizeof(Warn_restart));

> 
>   PG_RETURN_BYTEA_P(GET_BYTEA(trans));
> }
> 
> 8<--------------------------------
>