[GRASSLIST:10791] Re: How can I reduce the loading time of GRASS-layers in UMN Mapserver

[Radim Blazek]

On 3/7/06, wqual <wolfgang.qual at gmx.net> wrote:
> Hi Radim,
> thanks for your reply.
> Am Dienstag 07 März 2006 pH:44:09 vormittags schrieb Radim Blazek:
> > GRASS does not save spatial index in file becouse it
> > occupied too much space and spatial index is used only occasionly.

> This means that it is possible to create this spatial index?

Spatial index is created on-the-fly if necessary.

> > So spatial index could make it slower but 6 times seems too much.
> >
> > My guess is that it is caused by attributes. Try to go to the
> > vector directory in GRASS and rename temporarily 'dbln' file.

> Ok. Loading time decreased significantly. But no dbln, no queries (or am I
> wrong?). Mapserver-Maps should be queriable _and_ fast.

DBF driver in GRASS creates copy of the table in memory.
Try to use Postgres and SQLite. Postgres library also loads
all results to memory  by default.

Unfortunattely GetFeature in OGR reads both geometry and
attributes even if the attributes are not required by application.

Try also to compare time for GRASS and Shapefile if you use attributes
query.

BTW: Attribute queries are passed to GRASS database backend.

Radim

> > Also for testing to avoid the difference between nature
> > of topological and SF format try to test with points or lines.
> I did not test this by now.
>
> Best regards,
>
> Wolfgang
>
> ---8<-----------------
> >
> > Radim
> >
> > On 3/6/06, Wolfgang Qual <Wolfgang.Qual at gmx.net> wrote:
> > > Dear list,
> > > I created a mapfile for two identical themes: One of them is a shapfile,
> > > the other one is a grass vector dataset. The shapefile contains a
> > > *.qix-file which was created using the program shptree.
> > > I compared the loading time for the two themes using the command "time
> > > wget -O /dev/null "http://path/to/the.map". Result: the grass theme took
> > > about 12 seconds (on a local machine), shapefile only 2s.
> > > My Question therefore: is there a possibility to speed up grass layers in
> > > the mapserver application (something like shptree does?)? The attribute
> > > table of the grass-theme is a (default) dbf-file.
> > >
> > > Declaration of the grass-layer in the mapfile:
> > >
> > > # OGR-Layer aus GRASS
> > > #_# START LAYER l8
> > > LAYER  NAME "l8"
> > > TYPE polygon
> > > STATUS ON
> > >     CONNECTIONTYPE OGR
> > >     CONNECTION
> > > "/home/wqual/grassdata/muenchen/stadtbezirk/vector/block/head"
> > >     DATA "1"
> > >     METADATA
> > >       LTITLE "l8"
> > >     END #metadata
> > > ### TYPE Polygon -- LEGTYPE 0x01 -- SYMTYPE 0x02
> > > ### singlepolyleg
> > >    CLASSITEM "cat"
> > >    CLASS NAME "Block_GRASS"
> > >     COLOR 255 0 0
> > >     OUTLINECOLOR 20 200 10
> > >    END #CLASS
> > > #_# LAYER l8 QUERY
> > > END # LAYER l8
> > >
> > > I would be very happy to receive some hints/tips on this issue.
> > >
> > > Best regards,
> > >
> > > Wolfgang
> > >
> > > --
> > > Echte DSL-Flatrate dauerhaft für 0,- Euro*!
> > > "Feel free" mit GMX DSL! http://www.gmx.net/de/go/dsl
>