From fjoe@iclub.nsu.ru Tue Jan 23 03:38:45 2001
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Date: Tue, 23 Jan 2001 14:31:24 +0600 (NS)
From: Max Khon <fjoe@iclub.nsu.ru>
To: Bruce Momjian <pgman@candle.pha.pa.us>
cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Bug in FOREIGN KEY
In-Reply-To: <200101230416.XAA04293@candle.pha.pa.us>
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Status: RO

hi, there!

On Mon, 22 Jan 2001, Bruce Momjian wrote:

> 
> > This problem with foreign keys has been reported to me, and I have confirmed
> > the bug exists in current sources.  The DELETE should succeed:
> > 
> > ---------------------------------------------------------------------------
> > 
> > CREATE TABLE primarytest2 (
> >                            col1 INTEGER, 
> >                            col2 INTEGER, 
> >                            PRIMARY KEY(col1, col2)
> >                           );
> > 
> > CREATE TABLE foreigntest2 (col3 INTEGER, 
> >                            col4 INTEGER,
> >                            FOREIGN KEY (col3, col4) REFERENCES primarytest2
> >                          );
> > test=> BEGIN;
> > BEGIN
> > test=> INSERT INTO primarytest2 VALUES (5,5);
> > INSERT 27618 1
> > test=> DELETE FROM primarytest2 WHERE col1 = 5 AND col2 = 5;
> > ERROR:  triggered data change violation on relation "primarytest2"

I have another (slightly different) example:
--- cut here ---
test=> CREATE TABLE pr(obj_id int PRIMARY KEY);
NOTICE:  CREATE TABLE/PRIMARY KEY will create implicit index 'pr_pkey' for
table 'pr'
CREATE
test=> CREATE TABLE fr(obj_id int REFERENCES pr ON DELETE CASCADE);
NOTICE:  CREATE TABLE will create implicit trigger(s) for FOREIGN KEY
check(s)
CREATE
test=> BEGIN;
BEGIN
test=> INSERT INTO pr (obj_id) VALUES (1);
INSERT 200539 1
test=> INSERT INTO fr (obj_id) SELECT obj_id FROM pr;
INSERT 200540 1
test=> DELETE FROM fr;
ERROR:  triggered data change violation on relation "fr"
test=> 
--- cut here ---

we are running postgresql 7.1 beta3

/fjoe


From sszabo@megazone23.bigpanda.com Tue Jan 23 13:41:55 2001
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Date: Tue, 23 Jan 2001 10:41:21 -0800 (PST)
From: Stephan Szabo <sszabo@megazone23.bigpanda.com>
To: Bruce Momjian <pgman@candle.pha.pa.us>
cc: Jan Wieck <janwieck@Yahoo.com>, Peter Eisentraut <peter_e@gmx.net>,
        PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Bug in FOREIGN KEY
In-Reply-To: <200101230417.XAA04332@candle.pha.pa.us>
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> >     Think  I misinterpreted the SQL3 specs WR to this detail. The
> >     checks must be made per statement,  not  at  the  transaction
> >     level.  I'll  try  to fix it, but we need to define what will
> >     happen with referential actions in the  case  of  conflicting
> >     actions on the same key - there are some possible conflicts:
> > 
> >     1.  DEFERRED ON DELETE NO ACTION or RESTRICT
> > 
> >         Do  the referencing rows reference to the new PK row with
> >         the  same  key  now,  or  is  this  still  a   constraint
> >         violation?  I  would say it's not, because the constraint
> >         condition is satisfied at the end of the transaction. How
> >         do other databases behave?
> > 
> >     2.  DEFERRED ON DELETE CASCADE, SET NULL or SET DEFAULT
> > 
> >         Again  I'd  say  that  the  action  should  be suppressed
> >         because a matching PK row is present at transaction end -
> >         it's  not  the same old row, but the constraint itself is
> >         still satisfied.

I'm not actually sure on the cascade, set null and set default.  The
way they are written seems to imply to me that it's based on the state
of the database before/after the command in question as opposed to the
deferred state of the database because of the stuff about updating the
state of partially matching rows immediately after the delete/update of
the row which wouldn't really make sense when deferred.  Does anyone know
what other systems do with a case something like this all in a
transaction:

create table a (a int primary key);
create table b (b int references a match full on update cascade
		 on delete cascade deferrable initially deferred);
insert into a values (1);
insert into a values (2);
insert into b values (1);
delete from a where a=1;
select * from b;
commit;


From pgsql-hackers-owner+M3901@postgresql.org Fri Jan 26 17:00:24 2001
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Subject: Re: [HACKERS] Bug in FOREIGN KEY
In-Reply-To: <200101262110.QAA06902@candle.pha.pa.us> from Bruce Momjian at "Jan
	26, 2001 04:10:22 pm"
To: Bruce Momjian <pgman@candle.pha.pa.us>
Date: Fri, 26 Jan 2001 17:02:32 -0500 (EST)
CC: Jan Wieck <janwieck@Yahoo.com>, Peter Eisentraut <peter_e@gmx.net>,
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Bruce Momjian wrote:
> Here is another bug:
>
> test=> begin;
> BEGIN
> test=> INSERT INTO primarytest2 VALUES (5,5);
> INSERT 18757 1
> test=> UPDATE primarytest2 SET col2=1 WHERE col1 = 5 AND col2 = 5;
> ERROR:  deferredTriggerGetPreviousEvent: event for tuple (0,10) not
> found

    Schema?


Jan

--

#======================================================================#
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From pgsql-hackers-owner+M3864@postgresql.org Fri Jan 26 10:07:36 2001
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Date: Fri, 26 Jan 2001 16:07:27 +0100 (CET)
From: Peter Eisentraut <peter_e@gmx.net>
To: Hiroshi Inoue <Inoue@tpf.co.jp>
cc: Bruce Momjian <pgman@candle.pha.pa.us>,
        PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Open 7.1 items
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Hiroshi Inoue writes:

> What does this item mean ?
> Is it the following ?
>
> 	begin;
> 	insert into pk (id) values (1);
> 	update(delete from) pk where id=1;
> 	ERROR:  triggered data change violation on relation pk"
>
> If so, isn't it a simple bug ?

Depends on the definition of "bug".  It's not spec compliant and it's not
documented and it's annoying.  But it's been like this for a year and the
issue is well known and can normally be avoided.  It looks like a
documentation to-do to me.

-- 
Peter Eisentraut      peter_e@gmx.net       http://yi.org/peter-e/


From pgsql-hackers-owner+M3876@postgresql.org Fri Jan 26 13:07:10 2001
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From: "Mikheev, Vadim" <vmikheev@SECTORBASE.COM>
To: "'Jan Wieck'" <janwieck@Yahoo.com>,
        PostgreSQL HACKERS
  <pgsql-hackers@postgresql.org>,
        Bruce Momjian <root@candle.pha.pa.us>
Subject: RE: [HACKERS] Open 7.1 items
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> > FOREIGN KEY INSERT & UPDATE/DELETE in transaction "change violation"
> 
>     A well known issue, and I've asked multiple times how exactly
>     we want to define the behaviour for deferred constraints.  Do
>     foreign keys reference just to a key value and are happy with
>     it's existance, or do they refer to a particular row?

I think first. The last is closer to OODBMS world, not to [O]RDBMS one.

>     Consider you have a deferred "ON DELETE  CASCADE"  constraint
>     and  do  a  DELETE, INSERT of a PK. Do the FK rows need to be
>     deleted or not?

Good example. I think FK should not be deleted. If someone really
want to delete "old" FK then he can do 

DELETE PK;
SET CONSTRAINT ... IMMEDIATE; -- FK need to be deleted here
INSERT PK;

>     Consider you have a deferred "ON  DELETE  RESTRICT"  and  "ON
>     UPDATE  CASCADE" constraint. If you DELETE PK1 and UPDATE PK2
>     to PK1, the FK2 rows need to follow, but does PK2 inherit all
>     FK1 rows now so it's the master of both groups?

Yes. Again one can use SET CONSTRAINT to achieve desirable results.
It seems that SET CONSTRAINT was designed for these purposes - ie
for better flexibility.

Though, it would be better to look how other DBes handle all these
cases -:)

Vadim

From janwieck@yahoo.com Fri Jan 26 12:20:27 2001
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From: Jan Wieck <janwieck@yahoo.com>
Message-Id: <200101261730.MAA03196@jupiter.greatbridge.com>
Subject: Re: [HACKERS] Open 7.1 items
To: PostgreSQL HACKERS <pgsql-hackers@postgreSQL.org>,
        Bruce Momjian <root@candle.pha.pa.us>
Date: Fri, 26 Jan 2001 12:30:05 -0500 (EST)
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Bruce Momjian wrote:
> Here are my open 7.1 items.  Thanks for shrinking the list so far.
>
> ---------------------------------------------------------------------------
>
> FreeBSD locale bug
> Reorder INSERT firing in rules

    I  don't  recall  why this is wanted. AFAIK there's no reason
    NOT to do so, except for the actual state of beeing  far  too
    close to a release candidate.

> Philip Warner UPDATE crash
> JDBC LargeObject short read return value missing
> SELECT cash_out(1) crashes all backends
> LAZY VACUUM
> FOREIGN KEY INSERT & UPDATE/DELETE in transaction "change violation"

    A well known issue, and I've asked multiple times how exactly
    we want to define the behaviour for deferred constraints.  Do
    foreign keys reference just to a key value and are happy with
    it's existance, or do they refer to a particular row?

    Consider you have a deferred "ON DELETE  CASCADE"  constraint
    and  do  a  DELETE, INSERT of a PK. Do the FK rows need to be
    deleted or not?

    Consider you have a deferred "ON  DELETE  RESTRICT"  and  "ON
    UPDATE  CASCADE" constraint. If you DELETE PK1 and UPDATE PK2
    to PK1, the FK2 rows need to follow, but does PK2 inherit all
    FK1 rows now so it's the master of both groups?

    These  are  only two possible combinations. There are many to
    think of.  As said, I've asked before, but noone  voted  yet.
    Move  the item to 7.2 anyway, because changing this behaviour
    would require massive changes in the trigger queue *and*  the
    generic  RI triggers, which cannot be tested enough any more.


Jan

> Usernames limited in length
> Does pg_dump preserve COMMENTs?
> Failure of nested cursors in JDBC
> JDBC setMaxRows() is global variable affecting other objects
> Does JDBC Makefile need current dir?
> Fix for pg_dump of bad system tables
> Steve Howe failure query with rules
> ODBC/JDBC not disconnecting properly?
> Magnus Hagander ODBC issues?
> Merge MySQL/PgSQL translation scripts
> Fix ipcclean on Linux
> Merge global and template BKI files?
>
>
> --
>   Bruce Momjian                        |  http://candle.pha.pa.us
>   pgman@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
>


--

#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
# Let's break this rule - forgive me.                                  #
#================================================== JanWieck@Yahoo.com #


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