The current threading algorithm is applied to the entire result of a query, even
if maxnum is specified, and then the result of the threading algorithm is
truncated to maxnum. The improves threading results by returning the entire
thread even when only a single message makes it into the top maxnum results.
This commit applies the threading algorithm to the related message set of the
maxnum-truncated query result instead of to the entire query result. For a given
set of messages, the set of messages which will share threads with any of the
original messages is exactly the related message sets. Put another way, either
any messages returned by the original query but removed by the maxnum truncation
will also be returned by the related message query, or they would not have been
needed anyway because they would not be members of any visible thread.
To maintain backward compatibility and allow threading to be used without
including related messages, the related message set is found for the threading
calculation, but any messages which would not have matched the original query
are then pruned, resulting in a superset of the truncated query, but a subset of
the untruncated query.
This does not improve (or degrade) the run time of a threading calculation when
maxnum is not set, but significant improves it when maxnum is set by making it
scale (roughly) linearly in terms of maxnum. On a maildir with ~200k messages
and maxnum set to 500 (the default), the run time of a threading calculation is
lowered from ~1m to ~0.1s.
Perform threading calculation on related set instead of entire result.
The current threading algorithm is applied to the entire result of a query, even
if maxnum is specified, and then the result of the threading algorithm is
truncated to maxnum. The improves threading results by returning the entire
thread even when only a single message makes it into the top maxnum results.
This commit applies the threading algorithm to the related message set of the
maxnum-truncated query result instead of to the entire query result. For a given
set of messages, the set of messages which will share threads with any of the
original messages is exactly the related message sets. Put another way, either
any messages returned by the original query but removed by the maxnum truncation
will also be returned by the related message query, or they would not have been
needed anyway because they would not be members of any visible thread.
To maintain backward compatibility and allow threading to be used without
including related messages, the related message set is found for the threading
calculation, but any messages which would not have matched the original query
are then pruned, resulting in a superset of the truncated query, but a subset of
the untruncated query.
This does not improve (or degrade) the run time of a threading calculation when
maxnum is not set, but significant improves it when maxnum is set by making it
scale (roughly) linearly in terms of maxnum. On a maildir with ~200k messages
and maxnum set to 500 (the default), the run time of a threading calculation is
lowered from ~1m to ~0.1s.
We were transforming wild-card searches into regular-expression
searches; while that works, it's also significantly slower.
So, instead, special-case wildcards, and use the Xapian machinery for
wildcard queries.
In the olden days, we stored dates like e.g. 20180131121234, and do a
lexicographical check. With that, we could use e.g. upper-limits
201802312359 for "all dates in Feb 2018", even if Feb doesn't have 31
days.
However, nowadays we use time_t values, and g_date_time_new_local raises
errors for non-existent days; easiest fix is to massage things a bit; so
let's do that.
Fixes issue #1197.
For now, don't treat "and not" specially; this gets us back into a
somewhat working state. At some point, we probably _do_ want to
special-case and_not though (since Xapian supports it).
mu's query parser is the piece of software that turns your queries
into something the Xapian database can understand. So, if you query
"maildir:/inbox and subject:bla" this must be translated into a
Xapian::Query object which will retrieve the sought after messages.
Since mu's beginning, almost a decade ago, this parser was based on
Xapian's default Xapian::QueryParser. It works okay, but wasn't really
designed for the mu use-case, and had a bit of trouble with anything
that's not A..Z (think: spaces, special characters, unicode etc.).
Over the years, mu added quite a bit of pre-processing trickery to
deal with that. Still, there were corner cases and bugs that were
practically unfixable.
The solution to all of this is to have a custom query processor that
replaces Xapian's, and write it from the ground up to deal with the
special characters etc. I wrote one, as part of my "future, post-1.0
mu" reseach project, and I have now backported it to the mu 0.9.19.
From a technical perspective, this is a major cleanup, and allows us
to get rid of much of the fragile preprocessing both for indexing and
querying. From and end-user perspective this (hopefully) means that
many of the little parsing issues are gone, and it opens the way for
some new features.
From an end-user perspective:
- better support for special characters.
- regexp search! yes, you can now search for regular expressions, e.g.
subject:/h.ll?o/
will find subjects with hallo, hello, halo, philosophy, ...
As you can imagine, this can be a _heavy_ operation on the database,
and might take quite a bit longer than a normal query; but it can be
quite useful.
When you have multiple mu home directories, e.g. for the use case
detailed in my "Changing mu4e-{maildir,mu-home} from a context hook"
post to the mailing list it's quite inconvenient to have to hammer out
"mu --muhome=.. find .." every time you want to run some ad-hoc
command.
This allows me to set up a screen session where I do searches in mu
directory A in some screen panes, and searches in directory B in
others.
I initially called this MU_MUHOME but then I noticed that the perl
plugin has MUP_MU_HOME for analogous functionality, so I'm just
following its example.
The code I'm adding in mu-util.c is just a copy/paste & adjustment of
the same sort of already tested functionality in
mu_util_guess_maildir() just a few lines earlier.
