Thread

Re: [HACKERS] Re: [BUGS] General Bug Report: Bug in optimizer

Bruce Momjian <maillist@candle.pha.pa.us> — 1999-03-18T19:59:11Z

> Bruce Momjian wrote:
> > 
> > My guess is that the creation of the index updates the table size
> > statistics.
> 
> Yes.
> 
> > However, when I see zero size, I don't know if it is accurate, or if
> > someone has added rows since the last vacuum/index creation, so I think
> > it is correct to use an index on a zero-length table if it is
> > appropriate.  If the size is 1, I will assume that number is accurate,
> > and do a sequential scan.
> > 
> > Does that make sense?
> 
> Yes. But we have to fix SeqScan for field1 = -1...

The basic problem is that the -1 is stored as:
	
	{ EXPR 
	   :typeOid 0  
	   :opType op 
	   :oper 
	      { OPER 
	      :opno 558 
	      :opid 0 
	      :opresulttype 23 
	      }
	    
	   :args (
	      { CONST 
	      :consttype 23 
	      :constlen 4 
	      :constisnull false 
	      :constvalue  4 [  4  0  0  0 ]  
	      :constbyval true 
	      }
	   )

This is clearly undesirable, and causes the optimizer to think it can't
use the index.  

Is this bug report for 6.4.*, or did are you running the current
development tree?  I assume you are running 6.4.*, and am surprised this
did not show as a larger problem.

I will look in the grammer for a fix.  This should come across as a
single -4 constant.

-- 
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