top | item 45950720

Building a Simple Search Engine That Works

279 points| freediver | 4 months ago |karboosx.net | reply

79 comments

order
[+] marginalia_nu|4 months ago|reply
The idea behind search itself is very simple, and it's a fun problem domain that I encourage anyone to explore[1].

The difficulties in search are almost entirely dealing with the large amounts of data, both logistically and in handling underspecified queries.

A DBMS-backed approach breaks down surprisingly fast. Probably perfectly fine if you're indexing your own website, but will likely choke on something the size of English wikipedia.

[1] The SeIRP e-book is a good (free) starting point https://ciir.cs.umass.edu/irbook/

[+] djoldman|4 months ago|reply
> The difficulties in search are almost entirely dealing with the large amounts of data, both logistically and in handling underspecified queries.

Large amounts of data seem obviously difficult.

For your second difficulty, "handling underspecified queries": it seems to me that's a subset of the problem of, "given a query, what are the most relevant results?" That problem seems very tricky, partially because there is no exact true answer.

marginalia search is great as a contrast to engines like google, in part because google chooses to display advertisements as the most relevant results.

Have you found any of the TREC papers helpful?

https://trec.nist.gov/

[+] zipy124|4 months ago|reply
I think in today's world the harder problem is evading SEO spam. A search engine is in constant war with adverserarial players, who need you to see their content for revenue, rather than the actual answer.

This neccessitates a constant game of cat and mouse, where you adjust your quality metric so SEO shops can't figure it out and capitalise on it.

[+] mapt|4 months ago|reply
What is the order of magnitude of the largest document store that you can practically work from SQLite on a single thousand-dollar server run by some text-heavy business process? For text search, roughly how big of a corpus can we practically search if we're occupying... let's say five seconds per query, twelve queries per minute?
[+] submeta|4 months ago|reply
Thank you very much for the recommendation. I am in the process of building knowledge base bots, and am confronted with the task of creating various crawlers for the different sources the company has. And this book comes in very handy.
[+] gcanyon|4 months ago|reply
> The difficulties in search are almost entirely dealing with the large amounts of data, both logistically and in handling underspecified queries.

I would expect the difficulty to be deciding which item to return when there are multiple that contain the search term. Is wikipedia's article on Gilligan's Island better than some guy's blog post? Or is that guy a fanatic who has spent his entire life pondering whether Wrongway Feldman was malicious or how Irving met Bingo Bango and Bongo?

Add in rank hacking, keyword stuffing, etc. and it seems like a very hard problem, while scaling... is scaling? ¯\_(ツ)_/¯

[+] tombert|4 months ago|reply
About a decade ago, I was working with a guy who was getting a PhD in search engine design, which I knew/know nothing about.

It was actually a lot of fun to chat with him, because he was so enthusiastic about how searching works and how it can integrate with databases, and he was eager to explain this all to anyone who would listen. I learned a fair amount from him, though admittedly I still don't know much about the intricacies of how search engines work.

Some day, I am going to really go through the guts of Apache Solr and Lucene to understand the internals (like I did for Kafka a few years ago), and maybe I'll finally be competent with it.

[+] DanielHB|4 months ago|reply
People who work on really obscure things love to talk about their work, heck if someone would listen to me I could talk for hours about what I do.

Unfortunately very few people care about the minutia of making a behemoth system work.

[+] entropoem|4 months ago|reply
Searching in general is difficult. It is really a difficult thing.

If you haven't felt it, look at companies like Apple, Microsoft, or "The most important AI research lab in the world" OpenAI, for example, their products have terrible search features even though their resources - money - technology can be considered top-notch.

[+] marginalia_nu|4 months ago|reply
I think the reason most companies can't implement a working search box is the sort of work needed to make it perform adequately clashes catastrophically with the software development culture that has emerged in the corporate world (anything to do with sprints, jira, and daily standups).

Getting search to work well requires a lot of fiddling with ranking parameters, work that is difficult bordering on impossible to plan or track. The work requires a degree of trust that developers are rarely afforded these days.

[+] shortrounddev2|4 months ago|reply
idk if that argument really makes sense. A lot of AI chatbot companies have terrible or broken webapps and backend servers because it's not what they really care about. They put billions into their AI models, not their search features. I think the shittiness of their search features is symptomatic of the company's incentives, not necessarily the difficulty of the problem.
[+] franczesko|4 months ago|reply
Long time ago, I've really enjoyed a course by David Evans from Virginia University about building a search engine and concepts of computer science.

Building a "classic" search engine is a very fun project to go through.

https://www.cs.virginia.edu/~evans/courses/cs101/

List: https://www.youtube.com/watch?v=9nkR2LLPiYo&list=PLAwxTw4SYa...

Dave's profile: https://www.cs.virginia.edu/~evans/

[+] hammeiam|4 months ago|reply
I took this one as well - even as a new programmer is was really engaging and information-dense.
[+] precompute|4 months ago|reply
Incredible article. Does what it claims in the title, is written well and follows a linear chain of reasoning with a minumum of surprises.
[+] renegade-otter|4 months ago|reply
It's an interesting exercise. Having built searches before easily-available OSS products were available, and when even the commercial offerings sucked, do not ever build your a) database b) search engine, unless you can clearly state the reason for doing so.

Entire cubicle farms of people have been devoted to this problem for years, and if you dare to do this for work because "I think I can", you will find yourself in an ocean of hurt.

"Hey, so it won't be so hard to add 'did you mean' functionality, right? And we were thinking of adding a taxonomy next year for easy navigation..."

Check. Mate.

[+] nmstoker|4 months ago|reply
Reminds me of reading Programming Collective Intelligence by Toby Segaran, which inspired me with a range of things, like building search, recommenders, classifiers etc.
[+] _s_a_m_|4 months ago|reply
I loved that book also, but saw him a few year later saying in some youtube video "don't use that book" because it is obsolete in his opinion.
[+] cipherself|4 months ago|reply
That was a great book, I wonder what the 2025 equivalent of it is...
[+] eduction|4 months ago|reply
I completely agree with the insight that full text search has been complexified. People seem to want to jump straight to clustering or other enterprise level things.

I also appreciate the moxie of getting in there and building it yourself.

Myself, I reach for Lucene. Then you don’t need to build all this yourself if you don’t want. It lives in a dir on disk. True, it’s a separate database, but one optimized for this problem.

[+] aorloff|4 months ago|reply
This was the solution I was thinking about, but I thought, well that's the way someone would have done it 20 years ago
[+] wink|4 months ago|reply
My pet peeve for search engines for content I use is that they regularly ignore 2-letter and 3-letter "words" or acronyms. If all I need is a search for "mp3" then stripping exactly that is not useful ;) (was just the first file extension that came to my mind, but "PHP" works just as well).
[+] pelasaco|4 months ago|reply
love the style, colors and the cookie popup from https://karboosx.net/. Anyone knows if its an open source framework/style/tool being used here or it just the web dev skills of the author that are superb?
[+] mobeigi|4 months ago|reply
Great read. It makes you wonder how heavily optimised the tokenizers used by popular search enginea truly are.
[+] jillesvangurp|4 months ago|reply
Building a simple text search engine isn't that hard. People show them off on HN on a fairly regular basis. Most of those are fairly primitive. Unfortunately building a good search engine isn't that straightforward. There's more to it than just implementing bm25 (the goto ranking algorithm), which you can vibe code in a few minutes these days. The reason this is easy is because this is nineties era research that is all well publicized and documented and not all that hard once you figure it out.

Building your own search engine is a nice exercise for understanding how search works. It gets you to the same level as a very long tail of "Elasticsearch alternatives" that really aren't coming even close to implementing a tiny percentage of its feature set. That can be useful as long as you are aware of what you are missing out on.

I've been consulting companies for a few years with going from in house coded solutions to something proper (typically Opensearch/Elasticsearch). Usually people fight themselves into a corner where their in house solution starts simple and then grows more complicated as they inevitably deal with ranking problems their users encounter. Usual symptoms: "it's slow" (they are doing silly shit with multiple queries against postgres or whatever), "it's returning the wrong things" (it turns out that trigrams aren't a one size fits all solution and returns false positives), etc. Add aggregations and other things to the mix and you basically have a perfect use case for Elasticsearch about 10 years ago before they started making it faster, smarter, and better.

The usual arguments against Elasticsearch & Opensearch:

"Elasticsearch/Opensearch are hard to run". Reality, there isn't a whole lot to configure these days. Yes you might want to take care of monitoring, backups, and a few other things. As you would with any server product. But it self configures mostly. Particularly, you shouldn't have to fiddle with heap settings, garbage collection, etc. The out of the box defaults work fine. Get a managed setup if all this scares you; those run with the same defaults typically. Honestly, running postgres is harder. There's way more to configure for that. Especially for high availability setups. The hardest part is sizing your vms correctly and making sure you don't blow through your limits by indexing too much data. Most of your optimizations are going to be at the index mapping level, not in the configuration.

"It's slow". That depends what you do and how you use it. Most of the simple alternatives have some hard limitations. If you under engineer your search (poor ranking, lots of false positives) it's probably going to be faster. That's what happens if you skip all the fancy algorithmic stuff that could make your search better. I've seen all the rookie mistakes that people make with Elasticsearch that impact performance. They are usually fairly easy to fix. (e.g. let's turn off dynamic mapping and not index all those text fields you never query on that fill up your disk and memory and bloat your indexing performance ...).

"I don't need all that fancy stuff". Yes you do. You just don't know it yet because you haven't figured out what's actually needed. Look, if your search isn't great and it doesn't matter, it's all fine. But if search quality matters and you lose user's interest when they fail to find stuff in your app/website it quickly can become an existential problem. Especially if you have competitors that do much better. That fancy stuff is what you would need to build to solve that.

Unless you employ some hard core search ranking experts, your internally crafted thing is probably not going to be great. If you can afford to run at ~2005 era state of the art (Lucene existed, SOLR & Elasticsearch did not, Lucene was fairly limited in scope), then go for it. But it's going to be quite limited when you need those extra features after all.

There are some nice search products out there other than Elasticsearch & Opensearch that I would consider fit for purpose; especially if you want to do vector search. And in fairness, using a search engine properly still requires a bit of skill. But that isn't any different if you do things yourself. Except it involves a lot less wheel reinvention.

There just is a bit of necessary complexity to building a good search product.

[+] internet_points|4 months ago|reply
Seems like good advice, search has been built quite a few times now :-) I've defaulted to elasticsearch myself.

However, have you tried running any of the "up and coming" alternatives that keep showing up here? In particular, https://github.com/SeekStorm/SeekStorm seems very interesting, though I haven't heard from anyone using it in prod.

[+] hansvm|4 months ago|reply
> "I don't need all that fancy stuff". Yes you do.

> let's turn off dynamic mapping and not index all those text fields you never query on

[+] vivzkestrel|4 months ago|reply
what is your opinion about postgres full text search with tsvector, web_totsquery etc?
[+] nchmy|4 months ago|reply
what do you think about ManticoreSearch? It has been around longer than Lucene
[+] dominicrose|4 months ago|reply
I wonder how well it would scale. Elasticsearch's performance is impressive even at an unrecommended scale.
[+] journal|4 months ago|reply
why isn't there a place to post something where someone else will find it when searching that doesn't require auth? i get the logistics of what i'm asking, but i really think we need a global index.
[+] shevy-java|4 months ago|reply
Good. Now please someone replace Google's search engine.

I am always annoyed using it, how bad it is these days. Then I try the alternatives such as Duck Duck Go and they manage to be even worse.

Qwant is semi-ok but it also omits tons of things that Google Search finds (and also is slower, for some weird reason).

Google's UI nerf is also annoying - so much useless stuff. In the past I could disable that via ublock origin but Google killed that for chrome.

We need to do something against this Evil that Google brought into this world.

[+] ku1ik|4 months ago|reply
Try kagi.com. I tried and stayed. It’s paid though.
[+] MrAlex94|4 months ago|reply
Not quite independent as it’s a meta-search, but I developed a subscription based one at search.waterfox.net. Pays for the infrastructure costs and remains ad/tracking free.
[+] renegat0x0|4 months ago|reply
- How many people use only Google search engine nowadays? More and more people use chatbots, with Google search.

- Google search also does not provide good results for finding stuff in all walled gardens, so we also use niche search engines for individual platforms. I am not sure if it finds good results for posts in facebook and x.com

- I also use my own index of pages, YouTube channels, and github pages. Contains tags, page scoring system, related links, social information like number of followers etc.

https://github.com/rumca-js/Internet-Places-Database

So in a way, it has being replaced. It just takes some time for people to switch.