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Re: Simplify formatting.c

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: PostgreSQL-patches <pgsql-patches(at)postgresql(dot)org>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Euler Taveira de Oliveira <euler(at)timbira(dot)com>
Subject: Re: Simplify formatting.c
Date: 2008-06-23 02:21:19
Message-ID: 200806230221.m5N2LJI16272@momjian.us (view raw or flat)
Thread:
Lists: pgsql-patches
Bruce Momjian wrote:
> > Actually it seems like the hard part is not so much the input
> > representation as the output representation --- what should the
> > base-level initcap routine return, to be reasonably efficient for
> > both cases?
> 
> I hadn't gotten to trying it out yet, but I can see the output being a
> problem.  You can't even really pre-allocate the storage before passing
> it because you don't know the length after case change.  You could pass
> back a char* and repalloc to get the varlena header in there but that is
> very messy.
> 
> Add to that that the multi-byte case also has to be converted to wide
> characters, so you have text -> char * -> wide chars -> char * -> text
> for the most complex case.
> 
> I am starting to think that the simplest case is to keep the single-copy
> version in there for single-byte encodings and not worry about the
> overhead of the multi-byte case.

My new idea is if we pass the length to str_initcap, we can eliminate
the string copy from text to char *.  That leaves us with just one extra
string copy from char * to text, which seems acceptable.  We still have
the wide char copy but I don't see any easy way to eliminate that
because the multi-byte code is complex and not something we want to
duplicate.

-- 
  Bruce Momjian  <bruce(at)momjian(dot)us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

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

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