RE: Relevance search in Emacs

[Drew Adams <drew.adams@oracle.com>]

> Chapter 12. Full Text Search
> https://www.postgresql.org/docs/current/textsearch-intro.html*TEXTSEARCH-MATCHING

That's apparently what's often called full-text search,
and which is an indexed search.  The text is indexed
ahead of time, and the index is used for search "lookup".

It means that the text itself is not searched or searchable,
at least by those means, but it could of course be mixed
with a separate pass of actual search of the text (e.g.,
for regexp matching).

Typically words are indexed, along with their positions
(so nearness etc. can be among the search criteria).

> What is good is that database PostgreSQL offers built-in relevance
> searches..
> In the manual there is little I can find related to "relevance".

Which manual?

> If somebody knows if there is some "relevance" search in Emacs built-in
> packages let me know, otherwise I will let database do the job.

"Relevance" can mean anything.  Think of how much can go
into, say, a google search: "relevance" there can include
intimate detail about you as a person, your likes, etc.

Yes, some Emacs 3rd-party libraries do provide "scoring"
of some kinds of searches.  For example, for certain kinds
of fuzzy matching a score can indicate how "closely" a
given candidate is matched by your search pattern.

You'd do well, when looking for answers here or elsewhere,
to specify the kind of relevance you have in mind.

In general, it's up to you who define the search procedure
to define the relevant (!) relevance criteria, or those
that you make available to a user.