Bug in evaluation of AND

Started by Jeroen van Vianenalmost 28 years ago2 messages
#1Jeroen van Vianen
jeroenv@design.nl

[This email didn't show up on the list when I sent it last monday, so
here it is again].

Hi,

I found the following bug in sunday's snapshot (I am running Linux
2.1.85 and gcc 2.8.0):

I created a table with one column and inserted one row:

jeroenv=> create table test ( a int4 );
CREATE
jeroenv=> insert into test values ( 1 );
INSERT 321708 1

Some checks:

jeroenv=> select a from test where (a=1);
a
-
1
(1 row)

jeroenv=> select a from test where (a=1) and true;
a
-
1
(1 row)

Now, instead of column 'a' I return the constant 1:

jeroenv=> select 1 from test where (a=1);
?column?
--------
1
(1 row)

jeroenv=> select 1 from test where (a=1) and true;
?column?
--------
(0 rows)

No rows is not what I would expect.

However, with 'or' instead of 'and' returning a const value the query
works OK:

jeroenv=> select 1 from test where (a=1) or true;
?column?
--------
1
(1 row)

jeroenv=> select 1 from test where (a=1) or false;
?column?
--------
1
(1 row)

Cheers,

Jeroen van Vianen

#2Vadim B. Mikheev
vadim@sable.krasnoyarsk.su
In reply to: Jeroen van Vianen (#1)
Re: [HACKERS] Bug in evaluation of AND

Jeroen van Vianen wrote:

I found the following bug in sunday's snapshot (I am running Linux
2.1.85 and gcc 2.8.0):

Presents in 6.2.1 too...

Caused by bad execution plan:

Result (cost=0.00 size=0 width=0)
-> Seq Scan on aaa (cost=0.00 size=0 width=0)
^^^^^^^^^^^^^^^
Target list of SeqScan is empty => ExecProject returns NULL...
Optimizer should put Constant into Result' childplan target list
if it's empty. Easy to fix. Anyone ?

Vadim

Show quoted text

I created a table with one column and inserted one row:

jeroenv=> create table test ( a int4 );
CREATE
jeroenv=> insert into test values ( 1 );
INSERT 321708 1

Some checks:

jeroenv=> select a from test where (a=1);
a
-
1
(1 row)

jeroenv=> select a from test where (a=1) and true;
a
-
1
(1 row)

Now, instead of column 'a' I return the constant 1:

jeroenv=> select 1 from test where (a=1);
?column?
--------
1
(1 row)

jeroenv=> select 1 from test where (a=1) and true;
?column?
--------
(0 rows)

No rows is not what I would expect.