I see numerous mentions online of Vodka indexing with regard to PostgreSQL.
On the Wiki it's defined as,
(Korotkov) Vodka maintains two index files, one for keys and one for heap item pointers (postings). Each index file can be, in effect, managed by a different access method. This is a generalization of GIN, which uses btree (albeit its own btree code, not src/backend/access/nbtree) for both keys and postings. The keys index file has item pointers that refer to the postings index file. When the postings file's access method needs to move an index item, it must arrange to update any item pointer in the keys file. To that end, proposing a new "amupdateiptr" access method function. Calls to that function, when necessary, will arrive right after an amgettuple call.
Aside from that, you can see this post on the list
We are on the way to postgres-centric company and we'll continue our development in that company. We certainly don't need funding for the VODKA, our national product :) I thought about crowd-funding, but didn't find any good cases for products similar to postgres. So, we decided to go traditional way - built our own company and get money from industry. In short perspective we delay our development, since many-many other non-developers business, but in long perspective we'll have more russian contributors for the postgres project. Postgres in Russia was popular database, but now it gets much more interests from business and goverment, so I'm quite optimistic.
What ever happened to this and is it dead or did it get merged into something else?