[GRASS-dev] Output to Postgis Topology very slow

[Rémi Cura]

Update :
using v.build dump ,
importing it into postgres
parsing it to reconstitue tables (node, line, node-line_connection_info)
is about 10 sec(dump) +15 sec (import+parsing).
However if those table are functionnaly equivalent to postgis topology
(node, egde), I didn't write the conversion.

This figures seems to indicate that grass v.out.postgis topology=yes should
be about 5+10 sec (not 180 sec).

Is there any way to change the current behaviour to group the insert before
sending to data base
and/or
to just output grass topology table (node_grass, line_grass, area_grass,
isle_grass), so I could try batch conversion to postgis_topology?

Cheers,
Rémi-C


2014-05-07 17:37 GMT+02:00 Rémi Cura <remi.cura at gmail.com>:

>
>
>
> 2014-05-07 10:23 GMT+02:00 Moritz Lennert <mlennert at club.worldonline.be>:
>
> On 06/05/14 16:28, Rémi Cura wrote:
>>
>>> Hello everybody,
>>>
>>> I'm trying to track why converting from grass 7 vector to postgis
>>> topology vector is so slow.
>>> (http://trac.osgeo.org/postgis/ticket/2695), few sec to import it into
>>> grass , few sec to build topology in grass,*several minutes to push it*
>>>
>>> into PostGIS topology.
>>>
>>>
>>> So far I found that the only sql function used by grass are
>>> topology.createtopology
>>> topology.addtopogeometrycolumn
>>> topology.addnode
>>> topology.addedge
>>>
>>> I replaced the 2 last with empty function (returning 1) and that doesn't
>>> change the execution time (meaning slowness comes from grass side).
>>>
>>> My command lines executed on grass svn 7 on windows XP (server has
>>> latest postgres postgis geos gdal on ubuntu 12.04 virtual box) are:
>>>
>>> v.external.out dsn="PG:host=localhost dbname=test_grass port=5433
>>> user=postgres password=yourguess" format=PostgreSQL
>>> options="TOPOLOGY=yes,SCHEMA=test_route_utf8_4,TOPOSCHEMA_
>>> NAME=toposchema,TOPOGEOM_NAME=tg,TOPO_TOLERANCE=0.1,TOPO_
>>> GEO_ONLY=NO,SIMPLE_FEATURE=NO"
>>>
>>> time v.in.ogr dsn="....myshapefile.shp"
>>> -t output=test --overwrite
>>>
>>> _1. Can somebody please confirm that grass is building the topology on
>>> the vector layer *before* exporting it? (it seems to also build a
>>> topolgy *after *export)
>>>
>>>
>>> _2. I am under the impression that the conversion is slow because many
>>> queries are getting fired instead of few big ones. Is there any way to
>>> get tables in postgis with exact grass topology data (/point,line,called
>>> nodes,boundary,centroid,area,face/) to test batch conversion?
>>>
>>>
>> Have you tried v.out.postgis ?
>>
>>
>> Yes of course.
> I benched the following way :
>
> shapefile to postgres table
> no topology
> with attributes
> grass (v.external.out then v.in.ogr): about 40 sec
> grass (v.external.out (PG_USE_COPY=YES) then v.in.ogr): about 40 sec
> grass ( v.in.ogr then v.out.postgis ): about 40 sec
> grass ( v.in.ogr then v.out.ogr (PG_USE_COPY=NO)): about 30 sec
> grass ( v.in.ogr then v.out.ogr (PG_USE_COPY=YES)): about 4 sec
>
> ogr2ogr (PG_USE_COPY=YES)  : 4 sec
> ogr2ogr (PG_USE_COPY=NO)  : 30 sec
> shp2pgsql : 3 sec
>
> with topology
> grass (v.external.out (PG_USE_COPY=YES) then v.in.ogr ) : about 180 sec
> grass (v.external.out (PG_USE_COPY=NO) then v.in.ogr ) : about 180 sec
> grass ( v.in.ogr then v.out.postgis ) same.
>
>
> Cheers,
> Rémi-C
>
>
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