Re: Document "59.2. Built-in Operator Classes" have a clerical error?

Ah, seems Tom has even more detail so we will continue to discuss on
that thread.

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On Mon, Aug  3, 2020 at 07:51:51PM -0400, Bruce Momjian wrote:
> On Sun, Aug  2, 2020 at 08:43:53PM -0700, David G. Johnston wrote:
> > On Sun, Aug 2, 2020 at 8:17 PM osdba <mailtch@163.com> wrote:
> > 
> >     hi all:
> > 
> >     In Document "Table 59-1. Built-in GiST Operator Classes":
> > 
> >     "range_ops any range type && &> &< >> << <@ -|- = @> @>"， exist double "@>
> >     "，
> >      
> >     Should be "<@ @>" ?
> > 
> > 
> > 
> > It helps to reference the current version of the page (or provide a url link)
> > as that section seems to have migrated to Chapter 64 - though it is unchanged
> > even on the main development branch.
> > 
> > The table itself is extremely difficult to read: it would be more easily
> > readable if the font was monospaced, but its not.
> > 
> > I'm reasonably confident that the equal sign is part of the second-to-last
> > operator while the lone @> is the final operator.  Mostly I say this because
> > GiST doesn't do straight equality so a lone equal operator isn't valid.
> 
> I dug into this.  This query I think explains why the duplicate is
> there:
> 
>     SELECT oprname, oprleft::regtype, oprright::regtype, oprresult::regtype
>     FROM pg_am
>         JOIN pg_opclass ON opcmethod = pg_am.oid
>         JOIN pg_amop ON opcfamily = pg_amop.amopfamily
>         JOIN pg_operator ON amopopr = pg_operator.oid
>     WHERE amname = 'gist'
>         AND opcname = 'range_ops'
>     ORDER BY 1
> 
>      oprname | oprleft  |  oprright  | oprresult
>     ---------+----------+------------+-----------
>      &&      | anyrange | anyrange   | boolean
>      &<      | anyrange | anyrange   | boolean
>      &>      | anyrange | anyrange   | boolean
>      -|-     | anyrange | anyrange   | boolean
>      <<      | anyrange | anyrange   | boolean
>      <@      | anyrange | anyrange   | boolean
>      =       | anyrange | anyrange   | boolean
>      >>      | anyrange | anyrange   | boolean
> -->     @>      | anyrange | anyrange   | boolean
> -->     @>      | anyrange | anyelement | boolean
> 
> Notice that @> appears twice.  (I am not sure why @> appears twice in
> the SQL output, while <@ appears only once.)  The PG docs explain the
> duplicate:
> 
>     https://www.postgresql.org/docs/12/functions-range.html
> 
>     @>     contains range     int4range(2,4) @> int4range(2,3)     t
>     @>     contains element     '[2011-01-01,2011-03-01)'::tsrange @> '2011-01-10'::timestamp     t
>     <@     range is contained by     int4range(2,4) <@ int4range(1,7)     t
>     <@     element is contained by     42 <@ int4range(1,7)     f
> 
> There is an anyrange/anyrange version, and an anyrange/anyelement
> version of @> and <@.  Anyway, for the docs, I think we can either
> remove the duplicate entry, or modify it to clarify one is for
> anyrange/anyrange and another is for anyrange/anyelement.  I suggest the
> first option.
> 
> -- 
>   Bruce Momjian  <bruce@momjian.us>        https://momjian.us
>   EnterpriseDB                             https://enterprisedb.com
> 
>   The usefulness of a cup is in its emptiness, Bruce Lee
> 
> 
> 

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EnterpriseDB                             https://enterprisedb.com

  The usefulness of a cup is in its emptiness, Bruce Lee