Thread

Re: [BUGS] General Bug Report: palloc fails with lots of ANDs and ORs

Bruce Momjian <maillist@candle.pha.pa.us> — 1998-01-12T16:35:55Z

Try changing your OS default memory size.  Unsure how to do this under
AIX.

> 
> 
> ============================================================================
>                         POSTGRESQL BUG REPORT TEMPLATE
> ============================================================================
> 
> 
> Your name		: David Hartwig
> Your email address	: daveh@insightdist.com
> 
> Category		: runtime: back-end: SQL
> Severity		: serious
> 
> Summary: palloc fails with lots of ANDs and ORs
> 
> System Configuration
> --------------------
>   Operating System   : AIX 4.1
> 
>   PostgreSQL version : 6.2
> 
>   Compiler used      : native CC
> 
> Hardware:
> ---------
> RS 6000
> 
> Versions of other tools:
> ------------------------
> NA
> 
> --------------------------------------------------------------------------
> 
> Problem Description:
> --------------------
> The follow is a mail message describing the problem on the PostODBC mailing list:
> 
> 
> I have run across this also.   We traced it down to a failure in the PostgreSQL server.   This occurs under the following conditions. 
> 
>     1.  MS Access 
>     2.  Specify a multi-part key in the link time setup with postgresql 
>     3.  Click on table view. 
> 
> What happens is MS Access takes the following steps.   First it selects all possible key values for the table being viewed.   I
> suspect it maps the key values to the relative row position in the display.   Then it uses the mapping to generate future queries based
> on the mapping and the rows showing on the screen.   The queries take the following form: 
> 
>     SELECT  keypart1, keypart2, keypart3, col4, col5, col6 ... FROM example_table 
>     WHERE 
>         (keypart1 = row1keypartval1 AND  keypart2 = row1keypartval2 AND  keypart3 = row1keypartval3) OR 
>         (keypart1 = row2keypartval1 AND  keypart2 = row2keypartval2 AND  keypart3 = row2keypartval3) OR 
>             . 
>             .      --  28 lines of this stuff.   Why 28... Why not 28 
>             . 
>         (keypart1 = row27keypartval1 AND  keypart2 = row27keypartval2 AND  keypart3 = row27keypartval3) OR 
>         (keypart1 = row28keypartval1 AND  keypart2 = row28keypartval2 AND  keypart3 = row28keypartval3); 
>   
> 
> The PostgreSQL sever chokes on this statement claiming it is out of memory.  (palloc)  In this example I used a three part key.  I
> do not recall if a three part key is enough to trash the backend.  It has been a while.    I have tried sending these kinds of statements
> directly through the psql monitor and get the same result. 
> 
> 
> --------------------------------------------------------------------------
> 
> Test Case:
> ----------
> select c1, c1 c3, c4, c5 ... from example_table
> where
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something) or
> (c1 = something and c2 = something and c3 = something and c4 = something);
> 
> 
> --------------------------------------------------------------------------
> 
> Solution:
> ---------
> 
> 
> --------------------------------------------------------------------------
> 
> 
> 


-- 
Bruce Momjian
maillist@candle.pha.pa.us