I am using FTS5 for pretty complex search in my application, but recently, trying to make it even more complex I faced some problems that are more general than only FTS5.
I have a forum engine where are several tables for the threads, for the posts, for the users etc. At first I want to be able to search in the posts text, but moreover, this search have to be limiter to some subset of the posts, for example in the posts of a particular thread or posts of some user. Also, there are cases where free-text search is not actually necessary, for example when I am searching for all posts from a particular user. At first, I tried to create a FTS5 table, containing only the text data that need to be searched and then to access it by queries of the type: select some, fields from fts left join posts p on p.id = fts.rowid left join threads t on t.id = p.threadid left join users u on u.id = p.userid where fts match ?1 and u.nick = ?2 and t.id = ?3 order by ORDER Such queries are pretty fast when there is only fts match directive in the where clause. But any additional condition added ruins the performance, especially if the fts match returns big amount of matches. Additional problem is the order by clause. If the ORDER BY term is "rank" everything works great, but changing it to other field (for example the post time in order to get first most recent posts) causes huge slow down of the query. My second attempt was to sacrifice space for speed and to put all searchable data in the fts table - post text, the thread titles and the usernames. This way, building complex fts queries kind of: (content: ?1 OR caption: ?2) AND thread: ?3 AND user: ?4 I can leave only the fts query in the WHERE clause. This way, the search is pretty fast, but the huge problem remains the ORDER BY clause. Again everything works fine with "rank", but attempts to use any other field for sorting, causes huge probems: slow downs up to tens of seconds (usual search time is few milliseconds) and out of memory errors. Such problems with this second approach are even more serious than on the first approach. i.e. with the second approach everything works fine and quick with "rank" order by, and very, very slow and with errors, on any other "order by" option. So, he main question follows: What is the right way to design such complex search systems, based on FTS? How to properly approach the sorting of the search results in order to not have so big slowdowns and out of memory errors. Any tips are highly welcome! Regards -- http://fresh.flatassembler.net http://asm32.info John Found <johnfo...@asm32.info> _______________________________________________ sqlite-users mailing list firstname.lastname@example.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users