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From: Ron Clarke <rclarkeai@gmail.com>
Date: Wed, 20 Aug 2025 18:56:47 +0200
Message-ID: <CAGVf-sMLRbWsff5x3_s6vGisQCLy7LPTmJMOWoyaORy6yBC+Wg@mail.gmail.com>
Subject: Re: Domains vs data types
To: Greg Sabino Mullane <htamfids@gmail.com>
Cc: =?UTF-8?B?RXJ0YW4gS8O8w6fDvGtvZ2x1?= <ertan.kucukoglu@gmail.com>, 
	pgsql-general <pgsql-general@lists.postgresql.org>
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Opinion: domains are useful if you give them names that are full of
meaning. For example if you have the same type of data accross tables
"item_number" or "account" etc so that you can use them to describe what
you want stored in them and ensure the same defaults, nulls etc are applied
accross tables. Having randomly named or encoded lists just makes life more
complicated.

On Wed, 20 Aug 2025, 18:13 Greg Sabino Mullane, <htamfids@gmail.com> wrote:

> On Wed, Aug 20, 2025 at 12:48=E2=80=AFAM Ertan K=C3=BC=C3=A7=C3=BCkoglu <
> ertan.kucukoglu@gmail.com> wrote:
>
>> Does the second table have any technical advantage/disadvantage over
>> plain data type definition?
>> Less metadata in memory? High metadata in memory? Less/increased disk
>> space?
>>
>
> Same disk space. No disadvantage other than confusing your users, and any
> performance differences will be so minor as to be unmeasurable. (my two
> cents: domains are best when the data type is complex AND shared across
> multiple tables. Even then I tend to avoid them.)
>
> Cheers,
> Greg
>
> --
> Crunchy Data - https://www.crunchydata.com
> Enterprise Postgres Software Products & Tech Support
>
>

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<div dir=3D"auto">Opinion: domains are useful if you give them names that a=
re full of meaning. For example if you have the same type of data accross t=
ables &quot;item_number&quot; or &quot;account&quot; etc so that you can us=
e them to describe what you want stored in them and ensure the same default=
s, nulls etc are applied accross tables. Having randomly named or encoded l=
ists just makes life more complicated.</div><br><div class=3D"gmail_quote g=
mail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Wed, 20 Aug =
2025, 18:13 Greg Sabino Mullane, &lt;<a href=3D"mailto:htamfids@gmail.com">=
htamfids@gmail.com</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote=
" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><=
div dir=3D"ltr"><div dir=3D"ltr">On Wed, Aug 20, 2025 at 12:48=E2=80=AFAM E=
rtan K=C3=BC=C3=A7=C3=BCkoglu &lt;<a href=3D"mailto:ertan.kucukoglu@gmail.c=
om" target=3D"_blank" rel=3D"noreferrer">ertan.kucukoglu@gmail.com</a>&gt; =
wrote:</div><div class=3D"gmail_quote"><blockquote class=3D"gmail_quote" st=
yle=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padd=
ing-left:1ex"><div dir=3D"ltr"><div>Does the second table have any technica=
l advantage/disadvantage over plain data type definition?</div><div>Less me=
tadata in memory? High metadata in memory? Less/increased disk space?</div>=
</div></blockquote><div><br></div><div>Same disk space. No disadvantage oth=
er than confusing your users, and any performance differences will be so mi=
nor as to be unmeasurable. (my two cents: domains are best when the data ty=
pe is complex AND shared across multiple tables. Even then I tend to avoid =
them.)</div><div><br></div><div>Cheers,</div></div><div dir=3D"ltr" class=
=3D"gmail_signature"><div dir=3D"ltr"><div>Greg</div><div><br></div><div>--=
</div><div>Crunchy Data - <a href=3D"https://www.crunchydata.com" target=3D=
"_blank" rel=3D"noreferrer">https://www.crunchydata.com</a></div><div>Enter=
prise Postgres Software Products &amp; Tech Support</div><div><br></div></d=
iv></div></div>
</blockquote></div>

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