On Tue, Jan 5, 2010 at 3:58 AM, Leonardo F <m_li...@yahoo.it> wrote: >> You might want to search the archives (or the wiki history, or the CVS >> history if it's been there since before we moved the TODO list to the >> wiki) for discussion of why that item was added to the TODO in the >> first place. > > I read the thread: > > http://archives.postgresql.org/pgsql-hackers/2004-02/msg00478.php > > 1) it is true that "getbit sounds a lot like what substring() does", but the > same could be said for binary string substring/get_byte; so IMHO get/set_bit > should be present for bit string > 2) it is not very clear to me how "setbit could actually be handled by > replace()" (maybe "overlay" style?) > 3) since I'm looking at byte string get/set_bit to understand how that works, > I'm having a hard time understanding why the bit indexes in get/set_bit are > low-first based: > > select get_bit(E'\\376\\376'::bytea, s) as b,s from generate_series(0,15,1) > as s > b s > 0 0 > 1 1 > 1 2 > 1 3 > 1 4 > 1 5 > 1 6 > 1 7 > 0 8 > 1 9 > 1 10 > 1 11 > 1 12 > 1 13 > 1 14 > 1 15 > > > I understand this is the internal representation, but still: if someone asked > me what the 8th bit in 1111111011111110 is, I would have said 1, not 0 > (assuming the first bit has index '0'). Actually, David Helgason's patch > (http://archives.postgresql.org/pgsql-hackers/2004-01/msg00498.php) goes in > this direction: note the > > bitNo = 7 - (n % 8); > > part. Using that algorithm would mean get/set_bit in bit string would behave > differently from what they do in binary string (IMHO it's the binary string > implementation that is "wrong").
Well, I'm not really clear on what you're trying to accomplish here. As you say, there's really no point in changing the internal representation, and if you don't find replace() useful either, then why are you even working on this at all? Since the latest discussion of this is more than five years old, it's unclear that anyone even cares any more. It seems to me that making replace overlay a substring of bits could be a reasonable thing to do, but if nobody actually wants it, then the simplest thing to do is remove this from the TODO and call it good. ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
