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Re: bitmap AM design

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Victor Y(dot) Yegorov" <viy(at)mits(dot)lv>
Cc: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: bitmap AM design
Date: 2005-03-01 19:05:41
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Lists: pgsql-hackers
"Victor Y. Yegorov" <viy(at)mits(dot)lv> writes:
> All lists (list of ctids, bitmaps) will only grow, no data will be
> deleted, as deletes will require relocation and possibly exclusive
> lock on the index.
> Extending lists will need only a short-term exclusive locks on the pages in
> the tails of each list.

Hmm, you seem to be envisioning that these are actually lists, not
arrays --- that is, to find the N'th page in a list requires traversing
list links starting at the first page.  That doesn't sound workable.
If you can't access all the entries in roughly constant time then the
thing is going to have problems with big tables.

> I have counter question for you: you've mentioned, that you want bitmaps in
> the 8.1. What kind of bitmaps you were speaking about?

In-memory is what I intend to work on.

			regards, tom lane

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