> -----Original Message----- > From: Martijn van Oosterhout [mailto:kleptog@xxxxxxxxx] > Sent: Wednesday, October 19, 2005 2:46 PM > To: Dann Corbit > Cc: Terry Fielder; Tino Wildenhain; Marc G. Fournier; > Richard_D_Levine@xxxxxxxxxxxx; pgsql-hackers@xxxxxxxxxxxxxx; pgsql- > general@xxxxxxxxxxxxxx > Subject: Re: 'a' == 'a ' (Was: RE: [pgsql-advocacy] Oracle > buysInnobase) > > On Wed, Oct 19, 2005 at 02:05:20PM -0700, Dann Corbit wrote: > > > When the compared datatypes are VARCHAR: YES > > > > What is the value of doing that? > > > > I can see plenty of harm and absolutely no return. We are talking about > > blank padding before comparison. Do you really want 'Danniel ' > > considered distinct from 'Danniel ' in a comparison? In real life, > > what does that buy you? > > Well, looking from the point of view of using indexes, indexes can only > really match on things that are equal. Which means the system is going > to have to trim them anyway. I'm of the opinion that strings are > strings and spaces are no different from other characters. > > That bit of the standard quoted earlier, if you read the PAD character > that is different from any other character as being the NUL character, > then 'a<space><nul>' is clearly different from 'a<space><space>'. This > whacky space behaviour is something I associate with the char(N) and is > the main reason I never use it. > > > Perhaps this is old hat to the long-timers around here and there is a > > good explanation as to why varchar should have non-blank padding when > > comparisons are performed. Can someone point me to documentation that > > explains it? > > The way I understood it: > > char(N) is blank padding > varchar(N) is not > > If you make varchar(n) do blank padding, then what's the difference > between the two types? Storage. The blank padding is only for comparison purposes. >You may as well get rid of one... All the other database systems seem to handle it in the way that I expect. Which is not to say that it is the right way or that it agrees with the standard. But it is how it appears to me, so far. ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
