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* pl/pgsql, cursors and C function
@ 2003-09-23 11:41 Tomasz Myrta <jasiek@klaster.net>
2003-09-23 15:15 ` Re: pl/pgsql, cursors and C function Tom Lane <tgl@sss.pgh.pa.us>
0 siblings, 1 reply; 4+ messages in thread
From: Tomasz Myrta @ 2003-09-23 11:41 UTC (permalink / raw)
To: pgsql-sql
Hi
I'm making my first steps in C functions. I want to avoid doing all the
SQL job in them, pl/pgsql looks a better choice. I tried to do this by
passing opened cursor from pl/pgsql function to C function.
Here is simple C function:
#include <server/postgres.h>
#include <server/executor/spi.h>
PG_FUNCTION_INFO_V1(test2);
Datum test2(PG_FUNCTION_ARGS)
{
Portal p;
int n;
p=SPI_cursor_find("xxx");
if(!p)
elog(ERROR,"Cursor error");
SPI_cursor_fetch(p,true,1);
n=SPI_processed;
PG_RETURN_INT32(n);
}
And pl/pgsql one:
CREATE OR REPLACE FUNCTION test() returns integer AS '
DECLARE
_m CURSOR FOR select id from some_table limit 1;
n integer;
BEGIN
_m=''xxx'';
open _m;
n=test2();
close _m;
return n;
END;
' language 'plpgsql';
select test();
I don't understand ERROR message at all:
ERROR: SPI_prepare() failed on "SELECT $1 "
This error is raised when trying to execute SPI_cursor_fetch. What does
it mean? What does the SPI_prepare have to already opened cursor?
Where can I find better SPI documentation than "Postgresql Server
Programming" ?
Regards,
Tomasz Myrta
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: pl/pgsql, cursors and C function
2003-09-23 11:41 pl/pgsql, cursors and C function Tomasz Myrta <jasiek@klaster.net>
@ 2003-09-23 15:15 ` Tom Lane <tgl@sss.pgh.pa.us>
2003-09-23 16:43 ` Re: pl/pgsql, cursors and C function Tomasz Myrta <jasiek@klaster.net>
0 siblings, 1 reply; 4+ messages in thread
From: Tom Lane @ 2003-09-23 15:15 UTC (permalink / raw)
To: Tomasz Myrta <jasiek@klaster.net>; +Cc: pgsql-sql
Tomasz Myrta <jasiek@klaster.net> writes:
> I don't understand ERROR message at all:
> ERROR: SPI_prepare() failed on "SELECT $1 "
This is a bug. Or two bugs, actually: one of yours and one of PG's.
I have repaired the PG bug with the attached patch. The bug in your
code is that your C function needs to call SPI_connect and SPI_finish
if it's going to use any SPI operations.
regards, tom lane
inline patch 1: spi.c (+2/-1 lines) download inline-1.patch
Index: spi.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/executor/spi.c,v
retrieving revision 1.75.2.3
diff -c -r1.75.2.3 spi.c
*** spi.c 14 Feb 2003 21:12:54 -0000 1.75.2.3
--- spi.c 23 Sep 2003 15:09:39 -0000
***************
*** 1387,1393 ****
elog(ERROR, "invalid portal in SPI cursor operation");
/* Push the SPI stack */
! _SPI_begin_call(true);
/* Reset the SPI result */
SPI_processed = 0;
--- 1387,1394 ----
elog(ERROR, "invalid portal in SPI cursor operation");
/* Push the SPI stack */
! if (_SPI_begin_call(true) < 0)
! elog(ERROR, "SPI cursor operation called while not connected");
/* Reset the SPI result */
SPI_processed = 0;
* Re: pl/pgsql, cursors and C function
2003-09-23 11:41 pl/pgsql, cursors and C function Tomasz Myrta <jasiek@klaster.net>
2003-09-23 15:15 ` Re: pl/pgsql, cursors and C function Tom Lane <tgl@sss.pgh.pa.us>
@ 2003-09-23 16:43 ` Tomasz Myrta <jasiek@klaster.net>
2003-09-23 17:18 ` Re: pl/pgsql, cursors and C function Tom Lane <tgl@sss.pgh.pa.us>
0 siblings, 1 reply; 4+ messages in thread
From: Tomasz Myrta @ 2003-09-23 16:43 UTC (permalink / raw)
To: Tom Lane <tgl@sss.pgh.pa.us>; +Cc: pgsql-sql
>>I don't understand ERROR message at all:
>> ERROR: SPI_prepare() failed on "SELECT $1 "
>
>
> > This is a bug. Or two bugs, actually: one of yours and one of PG's.
> I have repaired the PG bug with the attached patch. The bug in your
> code is that your C function needs to call SPI_connect and SPI_finish
> if it's going to use any SPI operations.
>
> regards, tom lane
Thanks a lot. The first answer helped me, the second one - the others.
Do you know anything about good source of C functions documentation and
examples? Currently I'm walking over .h headers to find some useful
functions and macros.
Regads,
Tomasz Myrta
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: pl/pgsql, cursors and C function
2003-09-23 11:41 pl/pgsql, cursors and C function Tomasz Myrta <jasiek@klaster.net>
2003-09-23 15:15 ` Re: pl/pgsql, cursors and C function Tom Lane <tgl@sss.pgh.pa.us>
2003-09-23 16:43 ` Re: pl/pgsql, cursors and C function Tomasz Myrta <jasiek@klaster.net>
@ 2003-09-23 17:18 ` Tom Lane <tgl@sss.pgh.pa.us>
0 siblings, 0 replies; 4+ messages in thread
From: Tom Lane @ 2003-09-23 17:18 UTC (permalink / raw)
To: Tomasz Myrta <jasiek@klaster.net>; +Cc: pgsql-sql
Tomasz Myrta <jasiek@klaster.net> writes:
> Do you know anything about good source of C functions documentation and
> examples?
Look in the main sources (backend/utils/adt/, mostly) and/or contrib
modules for functions that do something like what you need. The only
difference between a builtin function and a dynamically loaded one is
you have to add the PG_FUNCTION_INFO macro.
regards, tom lane
^ permalink raw reply [nested|flat] 4+ messages in thread
end of thread, other threads:[~2003-09-23 17:18 UTC | newest]
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2003-09-23 11:41 pl/pgsql, cursors and C function Tomasz Myrta <jasiek@klaster.net>
2003-09-23 15:15 ` Tom Lane <tgl@sss.pgh.pa.us>
2003-09-23 16:43 ` Tomasz Myrta <jasiek@klaster.net>
2003-09-23 17:18 ` Tom Lane <tgl@sss.pgh.pa.us>
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