Here is a similar patch for org-clock's use of tags/properties matcher.

On Fri, Mar 16, 2012 at 12:31 AM, Ilya Shlyakhter <ilya_shl@alum.mit.edu>wrote:

> ,----
> | If your function needs to retrieve the tags including inherited tags
> | at the *current* entry,
>
> 'Function' here refers to the FUNC parameter of org-map-entries, not the
> MATCHER parameter.
> The matcher is constructed by org-make-tags-matcher, so we know everything
> it does --
> it does not move around and only asks about the current entry's tags and
> properties.
> org-scan-tags only invokes the matcher at the current entry, and sets
> org-scanner-tags
> correctly for that call.
>
> But, you're right that there is a problem: while org-scan-tags sets
> org-scanner-tags correctly
> before (eval matcher), other users of the matcher -- e.g.
> org-clock-get-table-data -- might not.
> So, org-trust-scanner-tags should be set not in the matcher, but in the
> function that calls
> the matcher.  A corrected patch is attached.
>
> thanks,
>
> ilya
>
>
> On Thu, Mar 15, 2012 at 11:13 PM, Nick Dokos <nicholas.dokos@hp.com>wrote:
>
>> Ilya Shlyakhter <ilya_shl@alum.mit.edu> wrote:
>>
>> > The attached patch speeds up tags matching ( 50s --> 5s for my most
>> > common search ), by turning on org-trust-scanner-tags within the
>> > matcher.
>> >
>> > (When it's off, getting a non-inherited property's value causes a call
>> > to org-entry-properties to fetch all properties into a cache,
>> > including ALLTAGS; fetching ALLTAGS involves calling
>> > (org-get-tags-at), which is slow when org-trust-scanner-tags is off.)
>> >
>> > Can this cause problems / was this off for a reason?
>> >
>>
>> I haven't looked at your patch carefully enough to know if it will or
>> will not cause problems, but check the doc for org-map-entries: it has
>> some guidelines about where the technique can be used and where it
>> cannot:
>>
>> ,----
>> | If your function needs to retrieve the tags including inherited tags
>> | at the *current* entry, you can use the value of the variable
>> | `org-scanner-tags' which will be much faster than getting the value
>> | with `org-get-tags-at'.  If your function gets properties with
>> | `org-entry-properties' at the *current* entry, bind
>> `org-trust-scanner-tags'
>> | to t around the call to `org-entry-properties' to get the same speedup.
>> | Note that if your function moves around to retrieve tags and properties
>> at
>> | a *different* entry, you cannot use these techniques.
>> `----
>>
>>
>> There are warnings that this variable is for internal dynamical scoping
>> only,
>> so I suspect you should not mess with the default. If your search can make
>> the needed guarantees, then you can just wrap it in a let to get the
>> speedup.
>> Otherwise, it probably should be left alone.
>>
>> Nick
>>
>>
>