Thread

1. Bug in evaluation of AND

   Jeroen van Vianen <jeroenv@design.nl> — 1998-02-18T08:57:21Z

   [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
   
   

2. Re: [HACKERS] Bug in evaluation of AND

   Vadim B. Mikheev <vadim@sable.krasnoyarsk.su> — 1998-02-18T10:53:11Z

   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
   
   > 
   > 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.