Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > Also, what does an in-memory bitmapped index look like?
>
> One idea that might work: a binary search tree in which each node
> represents a single page of the table, and contains a bit array with
> one bit for each possible item number on the page. You could not need
> more than BLCKSZ/(sizeof(HeapTupleHeaderData)+sizeof(ItemIdData)) bits
> in a node, or about 36 bytes at default BLCKSZ --- for most tables you
> could probably prove it would be a great deal less. You only allocate
> nodes for pages that have at least one interesting row.
Actually, I think I made a mistake. I was wondering what on-disk
bitmapped indexes look like.
-- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610)
359-1001+ If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square,
Pennsylvania19073
