Re: 9.1 - rewrite less alter table?

On Tue, Mar 08, 2011 at 10:43:55PM -0500, Noah Misch wrote:
> The patch optimizing that case foundered.  We may have it in 9.2.
> The current code only kicks in when the destination has no typmod.  When the
> source/destination type pair are marked "(binary coercible)" in the output of
> \dC, the optimization applies.  Alternately, it applies when one of the types is
> a constraint-free domain over the other.

ah, that explains it, thanks.

> The practical use cases are a bit thin at present.  The main interesting ones
> are varchar(N) -> text and conversions between domains and their base types.  We
> did these first because they required a proper subset of the code needed to
> support the more-common cases.
> The applicable definition of "binary coercible" appears in our CREATE CAST
> documentation.

thanks a lot for explanation. much clearer now.

Best regards,

depesz

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