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Re: string function - "format" function proposal

From: Itagaki Takahiro <itagaki(dot)takahiro(at)gmail(dot)com>
To: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
Cc: Alvaro Herrera <alvherre(at)commandprompt(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: string function - "format" function proposal
Date: 2010-09-01 00:53:44
Message-ID: AANLkTi=a6BAd6wTn2A6VVKmGwz4jThW8kRk+naDJARKd@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Wed, Sep 1, 2010 at 6:07 AM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
> I don't found a nice mix for placeholders and positional placeholders

How about %pos$format, used in C-printf()? It might be
only in Linux's libc.

printf("<%2$s> <%1$d>\n", 123, "abc");
=> <abc> <123>
http://linux.die.net/man/3/printf

> %i ... sql identifier
> %v ... sql value
> %s ... string --- the most used tag I expect
> %l ... literal

Looks good designed.  I have a couple of comments and questions:

* There is no examples for %l. What's the difference from %v and %s?
  If it always quotes, how does it work? Like as quote_literal()
  or quote_nullable()?

* %v quotes text values (and maybe all non-numeric values) with
  single quotes, but doesn't numeric values. How do we determine
  the difference? By type oid?

* %v also doesn't quote boolean values, but t and f are not valid.
  You should use true and false (or 't' and 'f') for the cases.
  (So, your "INSERT INTO" example is broken.)

-- 
Itagaki Takahiro

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