[GRASS-dev] t.list slow

[Radim Blazek]

On Sun, Oct 18, 2015 at 1:42 PM, Sören Gebbert
<soerengebbert at googlemail.com> wrote:
> Hi Radim,
> the reason why t.list and many other t.* modules are "slow" is the
> initialization of the temporal framework. Several background processes
> are started and the temporal databases are checked for each mapset in
> the mapset searchpath.

The time is almost constant regardless how many mapsets are in
SEARCH_PATH and still about 500ms if SEARCH_PATH is empty so it must
be something else.

> You have to use the GRASS GIS temporal framework directly to make it
> faster, so that the temporal framework is only initiated once and not
> every time a t.* module is called.

I would prefer to use it directly but I need a C API. Could be some
basic functions like get_dataset_list() ported to C library? If not,
is it some trick, some environment variable or something like that to
avoid unnecessary initialization, which could make it faster?

Radim

> I have implemented such a functionality here:
>  https://bitbucket.org/huhabla/grass-data-explorer/src/03e2fc5b74da163a2da5bfedca664afb542c4077/grassdataexplorerdialog.py?at=master&fileviewer=file-view-default#grassdataexplorerdialog.py-739
>
> The function from the temporal framework is: tgis.get_dataset_list()
> This should be almost as fast as the direct sqlite interface.
>
> Best regards
> Soeren
>
> 2015-10-18 13:15 GMT+02:00 Radim Blazek <radim.blazek at gmail.com>:
>> Hi,
>> I found t.list module to be quite slow, about 500ms. Simple "select *
>> from strds_absolute_time;" takes about 8ms with sqlite3 or db.select.
>> If I want to get list of more types for more mapsets (for example
>> mapsets which are not in SEARCH_PATH) it takes seconds.
>>
>> Is there a chance to make it faster?
>>
>> Radim