From: | Thom Brown <thom(at)linux(dot)com> |
---|---|
To: | Josh Berkus <josh(at)agliodbs(dot)com> |
Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: List of "binary-compatible" data types |
Date: | 2013-11-04 23:30:09 |
Message-ID: | CAA-aLv4Sqh9hdP=4=wrGHpUaZhGiQ-r0JjHxuoMvJYuwEZ8FNQ@mail.gmail.com |
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Lists: | pgsql-hackers |
On 4 November 2013 21:58, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> Folks,
>
> From our docs:
>
> "Adding a column with a non-null default or changing the type of an
> existing column will require the entire table and indexes to be
> rewritten. As an exception, if the USING clause does not change the
> column contents and the old type is either binary coercible to the new
> type or an unconstrained domain over the new type, a table rewrite is
> not needed ..."
>
> Which is nice, but nowhere do we present users with a set of
> binary-compatible data types, even among the built-in types. I'd
> happily write this up, if I knew what the binary-compatible data types
> *were*.
You could try this:
SELECT
castsource::regtype::text,
array_agg(casttarget::regtype order by casttarget::regtype::text) casttargets
FROM pg_cast
WHERE castmethod = 'b'
GROUP BY 1
ORDER BY 1;
--
Thom
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