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  1. bug? non working casts for domain

    Fabien COELHO <coelho@cri.ensmp.fr> — 2006-05-03T08:46:02Z

    Dear PostgreSQL developer.

Although it is allowed to create a cast for a domain, it seems that there 
is no way to trigger it. You can find attached an sql script to illustrate 
the issue with postgresql 8.1.3. The create cast and create domain 
documentations do not seem to discuss this point.

ISTM that it is a pg bug. Indeed, either

(1) the create cast should be rejected if it is not allowed for domains.

or

(2) the function should be triggered by explicit casts to the domain.

Have a nice day,

-- 
Fabien.

  2. Re: bug? non working casts for domain

    Bruce Momjian <pgman@candle.pha.pa.us> — 2006-05-06T23:10:07Z

    I can confirm that this is a bug.  The attached SQL shows that creating
a CAST _to_ a domain type doesn't work, though the cast can be created. 
The attached SQL provided by Fabien shows the failure.

The error is coming from parse_expr.c::typecast_expression, and its call
to typenameTypeId().  I wish I understood how we do domains better to
fix this properly.  Anyone?

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

Fabien COELHO wrote:
> 
> Dear PostgreSQL developer.
> 
> Although it is allowed to create a cast for a domain, it seems that there 
> is no way to trigger it. You can find attached an sql script to illustrate 
> the issue with postgresql 8.1.3. The create cast and create domain 
> documentations do not seem to discuss this point.
> 
> ISTM that it is a pg bug. Indeed, either
> 
> (1) the create cast should be rejected if it is not allowed for domains.
> 
> or
> 
> (2) the function should be triggered by explicit casts to the domain.

-- 
  Bruce Momjian   http://candle.pha.pa.us
  EnterpriseDB    http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +

  3. Re: bug? non working casts for domain

    Tom Lane <tgl@sss.pgh.pa.us> — 2006-05-07T02:19:39Z

    Bruce Momjian <pgman@candle.pha.pa.us> writes:
> The error is coming from parse_expr.c::typecast_expression, and its call
> to typenameTypeId().  I wish I understood how we do domains better to
> fix this properly.  Anyone?

The reason the cast isn't found is that find_coercion_pathway() strips
off the domains before it ever even looks in pg_cast.  We can't simply
remove that logic without breaking things (notably, the ability to cast
between a domain and its base type).  I think it would be a mistake to
consider this behavior in isolation anyway --- it's fairly tightly tied
to the way that domains are handled (or, mostly, ignored) in
operator/function lookup.  See recent gripes from Elein.

If someone can put together a coherent proposal for how domains should
be dealt with in operator/function resolution, I'm all ears.

			regards, tom lane

  4. Re: bug? non working casts for domain

    elein <elein@varlena.com> — 2006-05-08T18:15:04Z

    I'll see what I can do about expanding my requirements/test 
cases.  Casting was not in my original test cases.  
What else have I missed?  Copy domain gripes to elein@varlena.com.

--elein
elein@varlena.com



On Sat, May 06, 2006 at 10:19:39PM -0400, Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > The error is coming from parse_expr.c::typecast_expression, and its call
> > to typenameTypeId().  I wish I understood how we do domains better to
> > fix this properly.  Anyone?
> 
> The reason the cast isn't found is that find_coercion_pathway() strips
> off the domains before it ever even looks in pg_cast.  We can't simply
> remove that logic without breaking things (notably, the ability to cast
> between a domain and its base type).  I think it would be a mistake to
> consider this behavior in isolation anyway --- it's fairly tightly tied
> to the way that domains are handled (or, mostly, ignored) in
> operator/function lookup.  See recent gripes from Elein.
> 
> If someone can put together a coherent proposal for how domains should
> be dealt with in operator/function resolution, I'm all ears.
> 
> 			regards, tom lane
> 
> ---------------------------(end of broadcast)---------------------------
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> 
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  5. Re: bug? non working casts for domain

    Fabien COELHO <coelho@cri.ensmp.fr> — 2006-05-10T15:41:30Z

    > The reason the cast isn't found is that find_coercion_pathway() strips
> off the domains before it ever even looks in pg_cast.  We can't simply
> remove that logic without breaking things (notably, the ability to cast
> between a domain and its base type).  I think it would be a mistake to
> consider this behavior in isolation anyway --- it's fairly tightly tied
> to the way that domains are handled (or, mostly, ignored) in
> operator/function lookup.  See recent gripes from Elein.
>
> If someone can put together a coherent proposal for how domains should
> be dealt with in operator/function resolution, I'm all ears.

I would expect a DOMAIN to be a real plain type, and to have cast to 
and/or from its base type automatically created? The send/receive/in/out 
and so functions could be taken from the base type. All types could have a 
"check" function called on some occasions (well, each time one value is 
defined) when available to check for the validity of the value wrt the 
contraints, and that would be used by domains? If you do that, create
domain is just an alias for create type, and there is nothing special
about them one they are created.

But I think that it is maybe a little too simplistic and does not address 
the all relevant internal issues...

-- 
Fabien

  6. Re: bug? non working casts for domain

    Bruce Momjian <pgman@candle.pha.pa.us> — 2006-06-16T22:05:06Z

    Added to TODO list, with URL.

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

Fabien COELHO wrote:
> 
> Dear PostgreSQL developer.
> 
> Although it is allowed to create a cast for a domain, it seems that there 
> is no way to trigger it. You can find attached an sql script to illustrate 
> the issue with postgresql 8.1.3. The create cast and create domain 
> documentations do not seem to discuss this point.
> 
> ISTM that it is a pg bug. Indeed, either
> 
> (1) the create cast should be rejected if it is not allowed for domains.
> 
> or
> 
> (2) the function should be triggered by explicit casts to the domain.
> 
> Have a nice day,
> 
> -- 
> Fabien.

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-- 
  Bruce Momjian   http://candle.pha.pa.us
  EnterpriseDB    http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +