> 
> 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?

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?


darrenk

Tue, 6 Jan 1998 08:51:45 -0500
darrenk@insightdist.com (Darren King)
Re: [HACKERS] Block Sizes
> 
> > 
> > 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

Tue, 6 Jan 1998 10:18:18 -0500 (EST)
Bruce Momjian <maillist@candle.pha.pa.us>
Re: [HACKERS] Block Sizes