Re: [PATCH] tags search: faster tags matcher by trusting scanner tags

[Carsten Dominik <carsten.dominik@gmail.com>]

Hi Ilya, hi Nick,

thanks for looking into this.  I am amazed by the deep
understanding of Org's internals that shows in this
thread.

Both patches seem to be OK as far as I can see and
can be applied without adverse effects.
The patch for org-clock.el will at most achieve a factor
of two (because org-get-tags-at is called anyway), but
indeed, the patch in org.el can potentially have even
more significant effects, when properties are tested
in the matcher.

Cheers and thanks!

- Carsten

On 16.3.2012, at 05:34, Ilya Shlyakhter wrote:

> 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
> 
> 
> 
> <0003-Clocking-work-time-faster-filtering-of-clock-entries.patch>