Re: Time-correlated columns in large tables

On Tue, March 6, 2007 03:17, Heikki Linnakangas wrote:

> I think you've just described a range-encoded bitmap index. The idea is
> to divide the range of valid values into a some smallish number of
> subranges, and for each of these boundary values you store a bitmap
> where you set the bit representing every tuple with value < boundary
> value.

That's pretty cool!  From the looks of it, what you describe would solve
my problem--but using more storage in return for more flexibility.  My
scheme really required a correlation between a value and storage order,
which can be pretty fragile.  These range-encoded bitmap indexes wouldn't
have that problem.

I guess if you did simple run-length compression on these bitmaps you'd
end up more or less where I came in.  But you wouldn't want to flip a bit
somewhere in the middle of a compressed data stream, of course. :-)


Jeroen