@WeiZhong: I just noticed that Approach0 now also returns results from artofproblemsolving. Is there an option to restrict the search to a specific site (such as MSE)? That would be useful when checking if a question has been asked before on this site (and can possibly be closed as a duplicate).

Btw, the Guide still states that only MSE is indexed.

@MartinR Currently there is no way to filter results like that. I will consider adding support for that later. And I am going to update documentation and the user guide very soon.

@Sil Right, your previous comment also addressed this point, I will keep it in mind.

The general solution is still to have an option on what additional fields/properties a post/document you want to index, and then those fields can be searched/filtered. Examples are tag, source name, rating or something like that.

And we will also need to add Boolean operator on keywords, such that we can ask search engine to return posts with a field required to have some keywords, or must not have that keywords. By doing so we will also be able to add filter on field, for example. I imagine a keyword like "-source:aops" will do the job that filters out AoPS posts, or "+source:mse" will require all the search results being from MSE. (I just have made up for my imagined Boolean query format)

I guess this approach is flexible and scalable.

Right. By the way, wasn't there previously an icon to navigate to the approach0 twitter account? I don't see any icons now at approach0.xyz/search, while after searching some icons appear at the bottom right, but when clicking the twitter account it wants me to tweet something.

The front page (when you not searching anything yet) has an icon at the bottom, it has twitter account link.

Oh I see the approach icon links to twitter, didn't notice that before.

@Sil I have added a few words regarding to the reason I choose to close source approach0 and what you should be aware when you share the private code: github.com/approach0/search-engine#updates-may-24-2019. I hope it makes sense to you. Just make sure do not overly distribute the code and the sharing of code can benefit contributors of Approach0 as a whole.

@MartinSleziak Let me know if you would like to be invited into the private repo. I would love to have you there so you can access the latest lexer/parser and it will help to figure out why some queries perform in certain way. Of course, only if you have Github account.

I do not have Github account. If/when I'll create one someday, I will ask. But I don't plan to start with github soon - I might be busy with other stuff in the next few months.

In any case, thanks for thinking of me!

Sure, thank you for all your help too!