Re: WIP: BRIN multi-range indexes

Hi,

attached is a patch series that includes both the BRIN multi-range
minmax indexes discussed in this thread, and the BRIN bloom indexes
initially posted in [1].

It seems easier to just deal with a single patch series, although we may
end up adding just one of those proposed opclasses.

There are 4 parts:

0001 - Modifies bringetbitmap() to pass all scan keys to the consistent
function at once. This is actually needed by the multi-minmax indexes,
but not really required for the others.

I'm wondering if this is a safechange, considering it affects the BRIN
interface. I.e. custom BRIN opclasses (perhaps in extensions) will be
broken by this change. Maybe we should extend the BRIN API to support
two versions of the consistent function - one that processes scan keys
one by one, and the other one that processes all of them at once.

0002 - Adds BRIN bloom indexes, along with opclasses for all built-in
data types (or at least those that also have regular BRIN opclasses).

0003 - Adds BRIN multi-minmax indexes, but only with float8 opclasses
(which also includes timestamp etc.). That should be good enough for
now, but adding support for other data types will require adding some
sort of "distance" operator which is needed for merging ranges (to pick
the two "closest" ones). For float8 it's simply a subtraction.

0004 - Moves dealing with IS [NOT] NULL search keys from opclasses to
bringetbitmap(). The code was exactly the same in all opclasses, so
moving it to bringetbitmap() seems right. It also allows some nice
optimizations where we can skip the consistent() function entirely,
although maybe that's useless. Also, maybe the there are opclasses that
actually need to deal with the NULL values in consistent() function?

regards

[1]
https://www.postgresql.org/message-id/5d78b774-7e9c-c94e-12cf-fef51cc89b1a%402ndquadrant.com

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Tomas Vondra http://www.2ndQuadrant.com
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