Re: Problem returning strings with pgsql 8.3.x

On Tue, May 13, 2008 at 8:01 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Martijn van Oosterhout <kleptog@svana.org> writes:
>  > On Mon, May 12, 2008 at 11:23:17PM -0600, Josh Tolley wrote:
>  >> SPI_push();
>  >> retval =
>  >> InputFunctionCall(&flinfo, lolVarGetString(returnVal, true),
>  >> resultTypeIOParam, -1);
>  >> SPI_pop();
>
>  > Won't this cause the return value to be allocated inside a new memory
>  > block which gets freeds at the SPI_pop?
>
>  The SPI_pop in itself is harmless ... the problem is the SPI_finish
>  further down, which will release all simple palloc's done within the
>  SPI function context.  What he needs is something comparable to this bit
>  in plpgsql:
>
>             /*
>              * If the function's return type isn't by value, copy the value
>              * into upper executor memory context.
>              */
>             if (!fcinfo->isnull && !func->fn_retbyval)
>             {
>                 Size        len;
>                 void       *tmp;
>
>                 len = datumGetSize(estate.retval, false, func->fn_rettyplen);
>                 tmp = SPI_palloc(len);
>                 memcpy(tmp, DatumGetPointer(estate.retval), len);
>                 estate.retval = PointerGetDatum(tmp);
>             }
>
>  ie, push the data into something allocated with SPI_palloc().

I'll give this a shot as soon as I can... many thanks

>  I would bet large amounts of money that the problem is not "new in
>  8.3.0", either.  Perhaps Josh was not testing in an --enable-cassert
>  (CLOBBER_FREED_MEMORY) build before.

I'll check... that's definitely not unlikely. Again, thanks.

- Josh