Previously, we made each full-text search query a single prefix query.
That means that the query "do c" would turn into "do c*". That means it
would match "do cat" but not "dog cat".
Now, we make each token a prefix query. So "do c" would turn into
"do* c*". That means it would match both "do cat" and "dog cat".
Previously, if a message disappeared while looking at it in the search
results, it'd still stick around. Now they'll disappear from the results
in real-time.
I think I was initially lured into searching by rank because it gives
the illusion of providing the "best match". However, in practice, FTS
never gives back "bad" matches with low ranks -- all of the results it
returns will contain your query in some form (most commonly a direct
substring, but they do take some liberties if you have multiple tokens
in your queries). Given that, in general, more recent search results are
in fact more relevant, we can sort by date exclusively and get a better
ordering overall.
Previously, we'd always use the recipient of the message record, which
was incorrect for messages sent to groups. Now we always use the
recipient for the matching thread record.
Fixes#7823
