Re: More outdated examples

The following applied patch removes the section Tom thought wasn't
needed anymore.

---------------------------------------------------------------------------

Tom Lane wrote:
> Bruce Momjian  writes:
> > I can find no suitable replacement for this example.  Can anyone else?
> 
> > Peter Eisentraut wrote:
> >> This example in User's Guide section 7.2 doesn't work anymore at all:
> >> 
> >> tgl=> select @ text '-4.5' as "abs";
> 
> Both of the examples in this section have been obsoleted by our recent
> elimination of a lot of implicit casts.  This one would still work if
> text-to-float8 were an implicit cast, but it's not anymore.  Also,
> though the second one still acts as described, the reason given for it
> in the text is wrong: the system is not unable to choose among multiple
> alternatives.  Rather, it finds *no* alternatives, again because the
> text-to-various-int-types casts are no longer implicit.
> 
> The closest similar cases that I can find for the first example are not
> good replacements because they are also slated for destruction :-(.
> Basically, I see us moving away from the preferred-type mechanism, and
> perhaps eliminating it entirely soon.
> 
> I'd just remove the whole of Example 7.3, I think.  The mechanisms are
> still there, for now, but they are not invoked in any standard cases.
> 
> 			regards, tom lane
> 

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
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Index: doc/src/sgml/typeconv.sgml
===================================================================
RCS file: /cvsroot/pgsql-server/doc/src/sgml/typeconv.sgml,v
retrieving revision 1.27
diff -c -c -r1.27 typeconv.sgml
*** doc/src/sgml/typeconv.sgml	13 Mar 2003 01:30:29 -0000	1.27
--- doc/src/sgml/typeconv.sgml	19 Mar 2003 21:17:32 -0000
***************
*** 403,459 ****
  
  
  
- 
- Absolute-Value and Factorial Operator Type Resolution
- 
- 
- The PostgreSQL operator catalog has several
- entries for the prefix operator @</>, all of which implement
- absolute-value operations for various numeric data types.  One of these
- entries is for type float8, which is the preferred type in
- the numeric category.  Therefore, PostgreSQL
- will use that entry when faced with a non-numeric input:
- 
- SELECT @ '-4.5' AS "abs";
-  abs
- -----
-  4.5
- (1 row)
- 
- Here the system has performed an implicit conversion from text to float8
- before applying the chosen operator.  We can verify that float8 and
- not some other type was used:
- 
- SELECT @ '-4.5e500' AS "abs";
- 
- ERROR:  Input '-4.5e500' is out of range for float8
- 
- 
- 
- 
- On the other hand, the postfix operator !</> (factorial)
- is defined only for integer data types, not for float8.  So, if we
- try a similar case with !</>, we get:
- 
- SELECT '20' ! AS "factorial";
- 
- ERROR:  Unable to identify a postfix operator '!' for type 'text'
-         You may need to add parentheses or an explicit cast
- 
- This happens because the system can't decide which of the several
- possible !</> operators should be preferred.  We can help
- it out with an explicit cast:
- 
- SELECT CAST('20' AS int8) ! AS "factorial";
- 
-       factorial
- ---------------------
-  2432902008176640000
- (1 row)
- 
- 
- 
- 
  
  
  
--- 403,408 ----