pgbitmap

Announcing the first alpha release of pgbitmap, a bitmap type extension
for postgres.

This extension creates a space-optimised, non-sparse, bitmap type for
postgres.

A bitmap is an array of bits, indexed by an integer.  Bitmaps provide
an efficient means to implement sets and provide operations for:

- creating new bitmaps;
- adding an element to a bitmap;
- removing an element from a bitmap;
- testing for inclusion of an element in a bitmap;
- finding the minimum and maximum bits in the bitmap;
- unioning bitmaps together (set union/logical or);
- intersecting bitmaps (set intersection/logical and);
- subtracting one bitmap from another;
- converting bitmaps to and from textual representations;
- converting bitmaps to and from arrays;
- aggregating bits, and bitmaps, into bitmaps.

It differs from the standard Postgres bitstring in that it isn't based
around bit zero (bitmap(1000000) does not contain 1,000,000 zeroes
followed by a 1), and it has more functionality.  See the homepage on
github for more.

It was developed primarily in order to efficiently manage sets of
privileges for Virtual Private Database implementations.

It is hosted on github and can be found here:

https://github.com/marcmunro/pgbitmap

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Marc