Support for longer perceptive hashes

[pensnarik]

You extension is fine but it seems it only supports 64 bits perceptive hashes. But one might use a hash with a different length. For instance, in my application I use 256 bit hashes. Therefore I cannot use this extension to build indexes on them.

[stalkerg]

64bit probably because we can natively process it on modern CPU

[fake-name]

It's currently 64 bit because I can (ab)use inline storage for them. Postgresql itself uses 64-bit pointers, and you can just store your data right in what would be the pointer otherwise (all the <= 64-bit datatypes are implemented this way, actually).

There shouldn't be too much work to support out-of-line storage, though I'm super rusty about postgres dev stuff at the moment (see the failing tests too).

[Zer0-]

Is it possible to just use two columns to support 128bits? There would probably be a performance hit but it seems like that should work.

[fake-name]

As I understand it, using 2 columns wouldn't provide any guarantee that the two column's representations would be stored adjacent to each other on-disk. As such, you'd not have any advantage over out-of-line storage (which is the "correct" way to do this), and it would likely take a similar amount of effort.