Redis on steroids: Autocomplete using Redis, Nginx and Lua | Hacker News Reader

Redis on steroids: Autocomplete using Redis, Nginx and Lua

cucumbertown.com

64 pointsalagu11 comments

This implementation is too naive. You can't just autocomplete queries, you have to accept typos and errors and suggest the correct query. That's the hard part.

This is great need to figure out a good way to do request verification maybe to ensure the request it properly signed.

Update: this looks like a good article describing a verification scheme http://www.stavros.io/posts/writing-an-nginx-authentication-...

The usual implementation for autocomplete is to generate a trie data structure. A naive implementation will not have auto-correction or fix problems more established implementations have already addressed.

True, but tries do not automatically solve those problems, either, and most tries use lots of memory, especially on 64-bit systems (pointers, pointers everywhere!).

I'm currently implementing my own trie (for learning) for my own autocomplete module ... and I don't see how a trie (prefix tree) can solve the issues you just wrote.

It can't. You would have to fix the auto-correction before you searched the trie I'd think.

When you traverse the prefix tree and you are blocked: meaning, the prefix does not match an entry in the structure, you perform edit operations: insert, delete, transpose, and substitute. If one of those garners a match, you keep going down the tree until you reach your edit distance.

I love Redis, nginx, and Lua and wrote my own autocomplete implementation using Metaphone (e.g. https://github.com/threedaymonk/text) but after a while it became clear that what I really wanted was an instance of Solr.

I wonder if replacing nginx+lua with http://webd.is/ would be faster (and maybe easier to deploy)?

Could be.

We build something similar using node.js and it's working quite well. Perhaps we can open source that someday...

nginx+lua can be exceptionally fast. It's the basis for OpenResty, which is a consistent top-performer in the Web Framework Benchmarks (http://www.techempower.com/benchmarks/)

Webdis is a neat project, but I'd be a bit wary of deploying a custom HTTP server written just for Redis interactions. Nginx is battle-hardened.

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