Re: Question about indexes

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.

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