[PATCH] lib: make notmuch_query_count_messages exact

[Jani Nikula]

On Tue, 14 Oct 2014, Jani Nikula <jani at nikula.org> wrote:
> Our tests have expected this to be exact all along, but maybe
> inaccuracies only show up with big databases.

>From my IRC logs on Thu Oct 16 2014

j4ni   olly: does this do what it claims?
       http://mid.gmane.org/1413304374-17997-1-git-send-email-jani@nikula.org
olly   j4ni: not really
olly   if you don't set check at least it defaults to the number of
       requested matches
olly   so the code part is effectively a no-op
olly   but the reported number will be exact already so the comment
       changes are right
olly   i guess you could argue there's some merit in passing it explicitly
       in case someone decreases the request number of results

> ---
>  devel/TODO    | 5 -----
>  lib/notmuch.h | 6 +++---
>  lib/query.cc  | 7 ++++++-
>  3 files changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/devel/TODO b/devel/TODO
> index 1cf4089f1d93..116194d82ad1 100644
> --- a/devel/TODO
> +++ b/devel/TODO
> @@ -188,11 +188,6 @@ into the shared-library interface.
>  Audit all libnotmuch entry points to ensure that all Xapian calls are
>  wrapped in a try/catch block.
>  
> -Fix the "count" functionality to be exact as Olly explained in IRC:
> -
> -	ojwb> cworth: if you set the check_at_least parameter to the
> -	database size, get_matches_estimated() will be exact
> -
>  Fix the threading of a message that has a References: header but no
>  In-Reply-To: header (see id:"87lixxnxpb.fsf at yoom.home.cworth.org").
>  
> diff --git a/lib/notmuch.h b/lib/notmuch.h
> index dae041640fdb..6091082617e7 100644
> --- a/lib/notmuch.h
> +++ b/lib/notmuch.h
> @@ -893,10 +893,10 @@ void
>  notmuch_threads_destroy (notmuch_threads_t *threads);
>  
>  /**
> - * Return an estimate of the number of messages matching a search.
> + * Return the number of messages matching a search.
>   *
> - * This function performs a search and returns Xapian's best
> - * guess as to number of matching messages.
> + * This function performs a search and returns the number of matching
> + * messages.
>   *
>   * If a Xapian exception occurs, this function may return 0 (after
>   * printing a message).
> diff --git a/lib/query.cc b/lib/query.cc
> index 60ff8bd9a39e..ce26e3f3e4ed 100644
> --- a/lib/query.cc
> +++ b/lib/query.cc
> @@ -557,7 +557,12 @@ notmuch_query_count_messages (notmuch_query_t *query)
>  
>  	enquire.set_query (final_query);
>  
> -	mset = enquire.get_mset (0, notmuch->xapian_db->get_doccount ());
> +	/*
> +	 * Set the checkatleast parameter to the number of documents
> +	 * in the database to make get_matches_estimated() exact.
> +	 */
> +	mset = enquire.get_mset (0, notmuch->xapian_db->get_doccount (),
> +				 notmuch->xapian_db->get_doccount ());
>  
>  	count = mset.get_matches_estimated();
>  
> -- 
> 2.1.1