Обсуждение: possible mis-handling of nulls in views in 7.0.2

Hello,

   I'm running Postgres 7.0.2 and have run into a curious situation. I
got a back a null value in a select on VIEW that is defined as not
allowing that column to be null. Here's a screenshot:

marvel=> \d shipments;
View    = shipments
Query   = SELECT "web_data"."shipment_id", "web_data"."order_id",
"web_data"."customer_id", "web_data"."purchase_order_num", "web_data"."actual_ship
_date", "web_data"."pro_num", "sum"("web_data"."qt_ordered") AS
"qt_ordered", "sum"("web_data"."qt_shipped") AS "qt_shipped" FROM
"web_data" WHERE (
"web_data"."shipment_id" NOTNULL) GROUP BY "web_data"."shipment_id",
"web_data"."order_id", "web_data"."customer_id", "web_data"."actual_ship_date",
 "web_data"."pro_num", "web_data"."purchase_order_num";
+----------------------------------+----------------------------------+-------+
|              Field               |              Type                | Length|
+----------------------------------+----------------------------------+-------+
| shipment_id                      | varchar()                        |
  32 |
| order_id                         | varchar()                        |
 100 |
| customer_id                      | varchar()                        |
  10 |
| purchase_order_num               | varchar()                        |
 100 |
| actual_ship_date                 | date                             |
   4 |
| pro_num                          | varchar()                        |
 100 |
| qt_ordered                       | float8                           |
   8 |
| qt_shipped                       | float8                           |
   8 |
+----------------------------------+----------------------------------+-------+
marvel=>

### Notice that the shipment_id is NOTNULL
### now watch:

marvel=> select * from shipments where shipment_id is null;
shipment_id|order_id|customer_id|purchase_order_num|actual_ship_date|pro_num|qt_ordered|qt_shipped
-----------+--------+-----------+------------------+----------------+-------+----------+----------
           |        |           |                  |                |
   |          |
(1 row)
#############
It returns a row with a null shipment id!

I'm not sure what's happening here-- I tried to simplify this to a
simple case, but I couldn't reproduce the bug. Oddly, this null row
doesn't seem to appear in the table web_data that the view references. I
think it's easy enough to work around, but I'm curious what might be
happening here.

Thanks,

  -mark

personal website             }      Summersault Website Development
http://mark.stosberg.com/    {      http://www.summersault.com/

Mark Stosberg <mark@summersault.com> writes:
>    I'm running Postgres 7.0.2 and have run into a curious situation. I
> got a back a null value in a select on VIEW that is defined as not
> allowing that column to be null.

I think this is an artifact of the curious (not to say broken)
implementation of views pre-7.1.  However, it's hard to tell for sure
because I can't reproduce your problem.  Are you sure you are running
7.0.2 and not something older?  Can you provide a self-contained
example?  My test went like this:

play=> select version();
                             version
------------------------------------------------------------------
 PostgreSQL 7.0.2 on hppa2.0-hp-hpux10.20, compiled by gcc 2.95.2
(1 row)

play=> create table foo (f1 int, f2 int);
CREATE
play=> insert into foo values(1,2);
INSERT 873546 1
play=> insert into foo values(1,3);
INSERT 873547 1
play=> insert into foo values(2,4);
INSERT 873548 1
play=> insert into foo values(2,5);
INSERT 873549 1
play=> create view v2 as select f1,sum(f2) from foo where f1 notnull group by f1;
CREATE 873571 1
play=> select * from v2 ;
 f1 | sum
----+-----
  1 |   5
  2 |   9
(2 rows)

play=> select * from v2 where f1 isnull;
 f1 | sum
----+-----
(0 rows)

            regards, tom lane

Tom,

  I tried to build a simple test case and I couldn't reproduce either.
I'm still actively working with that database, though-- If I run into it
again, and can reproduce a condensed case, I'll definitely submit it. It
sounds like views are being improved a good deal in 7.1, so perhaps my
oddity would be repaired anyway. Thanks for checking it out.

   -mark

http://mark.stosberg.com/


Tom Lane wrote:
>
> Mark Stosberg <mark@summersault.com> writes:
> >    I'm running Postgres 7.0.2 and have run into a curious situation. I
> > got a back a null value in a select on VIEW that is defined as not
> > allowing that column to be null.
>
> I think this is an artifact of the curious (not to say broken)
> implementation of views pre-7.1.  However, it's hard to tell for sure
> because I can't reproduce your problem.  Are you sure you are running
> 7.0.2 and not something older?  Can you provide a self-contained
> example?  My test went like this:
>
> play=> select version();
>                              version
> ------------------------------------------------------------------
>  PostgreSQL 7.0.2 on hppa2.0-hp-hpux10.20, compiled by gcc 2.95.2
> (1 row)
>
> play=> create table foo (f1 int, f2 int);
> CREATE
> play=> insert into foo values(1,2);
> INSERT 873546 1
> play=> insert into foo values(1,3);
> INSERT 873547 1
> play=> insert into foo values(2,4);
> INSERT 873548 1
> play=> insert into foo values(2,5);
> INSERT 873549 1
> play=> create view v2 as select f1,sum(f2) from foo where f1 notnull group by f1;
> CREATE 873571 1
> play=> select * from v2 ;
>  f1 | sum
> ----+-----
>   1 |   5
>   2 |   9
> (2 rows)
>
> play=> select * from v2 where f1 isnull;
>  f1 | sum
> ----+-----
> (0 rows)
>
>                         regards, tom lane

--

http://mark.stosberg.com/