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Re: pgsql: If an index depends on no columns of itstable, give it a

From: Simon Riggs <simon(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-committers(at)postgresql(dot)org
Subject: Re: pgsql: If an index depends on no columns of itstable, give it a
Date: 2007-11-10 07:36:19
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Lists: pgsql-committers
On Fri, 2007-11-09 at 11:28 -0500, Tom Lane wrote:
> Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> > On Fri, 2007-11-09 at 04:05 -0500, Tom Lane wrote:
> >> That was my first reaction too, but the point about unique-index behavior
> >> refutes it.  Constraining a table to have at most one row is useful.
> > Sure is, and I've done it just a few days ago.
> > This SQL does it using standard syntax:
> >   create table foo (handle integer primary key check (handle = 1));
> That does not constrain the table to have only one row.  It constrains
> it to have only one value of the handle field (thereby making the field
> useless).  

It works, sure you need another column to put data in.

> The fact that there are workarounds isn't a reason to not
> support the index option.

The above is not a workaround. It is the SQL Standard way of solving the
problem, so why support another non-standard way?

Constants in indexes are just a strangeness we don't need. Supporting
weird syntax because one person wants it has never been anything you've
advocated before, so I'm surprised to see that argument deployed here.

  Simon Riggs

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