From: Adrian Klaver <adrian.klaver@gmail.com>
To: zoulx1982 <zoulx1982@163.com>
Subject: Re: type cast about int to bit
Date: Mon, 6 Feb 2012 19:28:55 -0800
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On Monday, February 06, 2012 6:42:45 pm zoulx1982 wrote:
> you mean there is no cast function for int  to varchar ?
> i see sure it is.
> 
That is why I said my guess:) If you want to see what is actually going on take 
a look at:
http://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/backend/utils/adt/varbit.c;h=adb08369ed28ab6b52aa2cd5213bcd5b4d8de7ad;hb=HEAD

The ERROR though is coming further up, in the parser , if I am following 
correctly.  This because as you have found out there is no direct cast from 
integer to varbit. Why that is for someone else to answer, as I don't know.

Though a little playing around got this, not pretty but it seems to work:

test(5432)aklaver=>SELECT 10::bit(3)::varbit(3);
 varbit 
--------
 010
(1 row)

test(5432)aklaver=>SELECT 10::bit(3)::varbit(4);
 varbit 
--------
 010
(1 row)

test(5432)aklaver=>SELECT 10::bit(4)::varbit(4);
 varbit 
--------
 1010
(1 row)

test(5432)aklaver=>SELECT 10::bit(4)::varbit(3);
 varbit 
--------
 101


-- 
Adrian Klaver
adrian.klaver@gmail.com