Re: What is the maximum encoding-conversion growth rate, anyway?

From: Michael Fuhr <mike(at)fuhr(dot)org>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Tatsuo Ishii <ishii(at)postgresql(dot)org>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: What is the maximum encoding-conversion growth rate, anyway?
Date: 2007-05-29 03:53:56
Message-ID: 20070529035356.GA67336@winnie.fuhr.org
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On Mon, May 28, 2007 at 10:23:42PM -0400, Tom Lane wrote:
> Tatsuo Ishii <ishii(at)postgresql(dot)org> writes:
> > I'm afraid we have to mke it larger, rather than smaller for 8.3. For
> > example 0x82f5 in SHIFT_JIS_2004 (new in 8.3) becomes *pair* of 3
> > bytes UTF_8 (0x00e3818b and 0x00e3829a). See
> > util/mb/Unicode/shift_jis_2004_to_utf8_combined.map for more details.
>
> > So the worst case is now 6, rather than 3.
>
> Yipes.

Isn't MAX_CONVERSION_GROWTH a multiplier? Doesn't 2 bytes becoming
2 * 3 bytes represent a growth of 3, not 6? Or does that 2-byte
SHIFT_JIS_2004 sequence have a 1-byte sequence in another supported
encoding? Or am I missing something?

--
Michael Fuhr

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