Thread

1. Re: [HACKERS] Large databases, performance

   Zeugswetter Andreas DCP SD <zeugswettera@spardat.at> — 2002-10-07T15:42:12Z

   > if i'm not mistaken, a char(n)/varchar(n) column is stored as a 32-bit
   > integer specifying the length followed by as many characters as the
   > length tells.  On 32-bit Intel hardware this structure is aligned on a
   > 4-byte boundary.
   
   Yes.
   
   > | opc0     char (3)   no    no       8     4
   > | opc1     char (3)   no    no       8     4
   > | opc2     char (3)   no    no       8     4
   
   > Hackers, do you think it's possible to hack together a quick and dirty
   > patch, so that string length is represented by one byte?  IOW can a
   > database be built that doesn't contain any char/varchar/text value
   > longer than 255 characters in the catalog?
   
   Since he is only using fixchar how about doing a fixchar implemetation, that 
   does not store length at all ? It is the same for every row anyways !
   
   Andreas
   
   

2. Re: [HACKERS] Large databases, performance

   Martijn van Oosterhout <kleptog@svana.org> — 2002-10-08T22:51:11Z

   On Mon, Oct 07, 2002 at 05:42:12PM +0200, Zeugswetter Andreas SB SD wrote:
   > > Hackers, do you think it's possible to hack together a quick and dirty
   > > patch, so that string length is represented by one byte?  IOW can a
   > > database be built that doesn't contain any char/varchar/text value
   > > longer than 255 characters in the catalog?
   > 
   > Since he is only using fixchar how about doing a fixchar implemetation, that 
   > does not store length at all ? It is the same for every row anyways !
   
   Remember that in Unicode, 1 char != 1 byte. In fact, any encoding that's not
   Latin will have a problem. I guess you could put a warning on it: not for
   use for asian character sets. So what do you do if someone tries to insert
   such a string anyway?
   
   Perhaps a better approach is to vary the number of bytes used for the
   length. So one byte for lengths < 64, two bytes for lengths < 16384.
   Unfortunatly, two bits in the length are already used (IIRC) for other
   things making it a bit more tricky.
   -- 
   Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
   > There are 10 kinds of people in the world, those that can do binary
   > arithmetic and those that can't.