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Re: Simplify formatting.c

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: PostgreSQL-patches <pgsql-patches(at)postgresql(dot)org>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Euler Taveira de Oliveira <euler(at)timbira(dot)com>
Subject: Re: Simplify formatting.c
Date: 2008-06-22 02:43:28
Message-ID: 200806220243.m5M2hS322144@momjian.us (view raw or flat)
Thread:
Lists: pgsql-patches
Tom Lane wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > Tom Lane wrote:
> >> I'd say not.  Can't we do some more refactoring and avoid so many
> >> useless conversions?  Seems like str_initcap is the wrong primitive API
> >> --- the work ought to be done by a function that takes a char pointer
> >> and a length.  That would be a suitable basis for functions operating
> >> on both text datums and C strings.
> 
> > Yea, I thought about that idea too but it is going to add a strlen()
> > calls in some places, but not in critical ones.
> 
> Sure, but the cost-per-byte of the strlen should be a good bit less than
> the cost-per-byte of the actual conversion, so that doesn't bother me
> too much.
> 
> 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 starto 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.

-- 
  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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Subject: A GUC variable to replace PGBE_ACTIVITY_SIZE
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