There is a bug in check_foreign_key of refint.c which is bundled with
the standard distribution. It occurs when a trigger calling this
function recursively fires another trigger which calls the same
function. The calling check_foreign_key loses its plan informantion and
when it tries to use it the backend closes its channel. You can check it
with the sql script I am attaching below.
The solution to this is to do a find_plan again before executing it at
line 483 of refint.c.
Therefore two more lines should be added before line 483:

sprintf(ident, "%s$%u", trigger->tgname, rel->rd_id);
plan = find_plan(ident, &FPlans, &nFPlans);

before line 483 which is:
  ret = SPI_execp(plan->splan[r], kvals, NULL, tcount);

Here is the script to check it:
create table a (
        a int4 primary key,
        b int4,
        c int4,
        d int4
        );

create table b (
        a int4 primary key,
        b int4,-- foreign key references a
        c int4,
        d int4
        );

create table ab (
        a int4 primary key,
        b int4,
        c int4,
        d int4
        );

create table bc (
        a int4 primary key,
        b int4,
        c int4,
        d int4
        );


create function check_primary_key()
        returns opaque
        as '/home/bye2data/postgresql-6.3.2/contrib/spi/refint.so'
        language 'c';

create function check_foreign_key()
        returns opaque
        as '/home/bye2data/postgresql-6.3.2/contrib/spi/refint.so'
        language 'c';

create trigger t1 before delete or update
        on a for each row execute procedure
        check_foreign_key(1,'cascade','a','b','b');

create trigger t2 before insert or update
        on b for each row execute procedure
        check_primary_key('b','a','a');

create trigger t3 before delete or update
        on ab for each row execute procedure
        check_foreign_key(2,'cascade','a','a','a','bc','a');

create trigger t4 before insert or update
        on a for each row execute procedure
        check_primary_key('a','ab','a');

create trigger t5 before insert or update
        on bc for each row execute procedure
        check_primary_key('a','ab','a');

insert into ab values(1,1,1,1);
insert into bc values (1,1,1,1);
insert into a values (1,1,1,1);
delete from ab where a=1;

Sorry for the confusing names of tables and attributes.

- Anand.


Fri, 02 Oct 1998 14:57:23 -0700
Anand Surelia <anand@bytekinc.com>
Bug in contrib/spi/refint.c
> There is a bug in check_foreign_key of refint.c which is bundled with
> the standard distribution. It occurs when a trigger calling this
> function recursively fires another trigger which calls the same
> function. The calling check_foreign_key loses its plan informantion and
> when it tries to use it the backend closes its channel. You can check it
> with the sql script I am attaching below.
> The solution to this is to do a find_plan again before executing it at
> line 483 of refint.c.
> Therefore two more lines should be added before line 483:
> 
> sprintf(ident, "%s$%u", trigger->tgname, rel->rd_id);
> plan = find_plan(ident, &FPlans, &nFPlans);
> 
> before line 483 which is:
>   ret = SPI_execp(plan->splan[r], kvals, NULL, tcount);

Please send a context diff to the patches list.


-- 
  Bruce Momjian                        |  http://www.op.net/~candle
  maillist@candle.pha.pa.us            |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026


Fri, 2 Oct 1998 18:36:07 -0400 (EDT)
Bruce Momjian <maillist@candle.pha.pa.us>
Re: [GENERAL] Bug in contrib/spi/refint.c