Thread

Re: [HACKERS] Block Sizes

Bruce Momjian <maillist@candle.pha.pa.us> — 1998-01-06T15:18:18Z

> 
> > 
> > How hard would it be for postgresql to support adjustable block sizes? 
> > Just wondering.
> > 
> 
> I can take a stab at this tonite after work now that the snapshot is there.
> Still have around some of the files/diffs from looking at this a year ago...
> 
> I don't think it will be hard, just a few files with BLCKSZ/MAXBLCKSZ
> references to check for breakage.  Appears that only one bit of lp_flags is
> being used too, so that would seem to allow up to 32k blocks.
> 
> Other issue is the bit alignment in the ItemIdData structure.  In the past,
> I've read that bit operations were slower than int ops.  Is this the case?

Usually, yes.

> 
> I want to check to see if the structure is only 32 bits and not being padded
> by the compiler.  Worse to worse, make one field of 32 bits and make macros
> to access the three pieces or make lp_off & lp_len shorts and lp_flags a char.
> 
> I can check the aix compiler, but what does gcc and other compilers do with
> bit field alignment?

I don't know.

-- 
Bruce Momjian
maillist@candle.pha.pa.us