[postgis-users] query multipolygon

[sgrocho2]

Postgis_full_version() returned:
"POSTGIS="1.3.5" GEOS="3.0.3-CAPI-1.4.2" PROJ="Rel. 4.6.1, 21 August 2008"
USE_STATS"

Yes we can share some data with you.  What is the easiest way to send you a
couple of tables from PostGIS?


Paul Ramsey-4 wrote:
> 
> Can you share this test data with me? (Just enough to demonstrate the
> condition.) What does your postgis_full_version() return?
> 
> P
> 
> On Tue, Jun 2, 2009 at 2:08 PM, sgrocho2 <sgrocho at gmail.com> wrote:
>>
>> Okay, I did run ST_IsValid() and everything from each of the layers
>> returned
>> a t.  When visually checking the query results with 167 rows it appears
>> that
>> the query is only returning rows that intersect the first polygon it
>> processes.  Leaving out those rows that only intersect the other 5
>> polygons.
>> The following image is an example of what is being missed.  The polygons
>> outlined in blue are not selected by the query since they only touch one
>> of
>> the parcel polygons(green).
>> http://www.nabble.com/file/p23840915/missed_features.jpg
>>
>>
>>
>>
>> Paul Ramsey-4 wrote:
>>>
>>> Slow-vs-fast I can understand... the spatial index can more
>>> effectively parcel out the problem for processing when the units of
>>> processing are smaller.
>>>
>>> Wrong-vs-right I have a problem with. Are your multi-polygons valid?
>>> Run ST_IsValid() on them. It's possible that they are valid taken
>>> separately but invalid when combined (multipolygons are not allowed to
>>> have overlapping components).
>>>
>>> Paul
>>>
>>> On Tue, Jun 2, 2009 at 11:05 AM, sgrocho2 <sgrocho at gmail.com> wrote:
>>>>
>>>> I am having trouble querying a multipolygon feature intersection with
>>>> another
>>>> multipolygon feature.  When I execute the query it takes 45 seconds and
>>>> returns and incomplete answer, 167 rows.  If I explode the parcel
>>>> polygon
>>>> into its 6 parts and then run the same query it takes 5 seconds and
>>>> returns
>>>> 209 rows which is the correct answer.  Is there a way to write this
>>>> query
>>>> to
>>>> return the all the rows without having to first manipulate the data?
>>>>  The
>>>> same query works fine in SQL Server but we want to use PostGIS. Below
>>>> is
>>>> the
>>>> code for each of the Parcel tables they include only one parcel - one
>>>> with 1
>>>> row, the other with 6 rows.
>>>>
>>>> THIS IS THE SINGLE FEATURE MULTIPOLYGON CODE: 45sec 167 rows
>>>> SELECT DISTINCT g1.objectid As taxpar_id, g1.tax_parcel_num As
>>>> parcel_number, g2.objectid As fw_id, g2.wdfw_phs, g2.wdfw_occur_pt,
>>>> g2.wdfw_haulout, g2.pc_for_fish, g2.wdfw_fish_dist, g2.pc_oaks,
>>>> g2.pc_salmon, g2.wdfw_occur_pl, g2.doh_sf, g2.wdfw_owl, g2.pc_eelgrass,
>>>> g2.pc_hydro, g2.wdfw_sasi
>>>>        FROM loader.single_parcel As g1,
>>>> loader.potential_fw_habitat_cons_areas_pg
>>>> As g2
>>>>    WHERE (g1.tax_parcel_num = '0618161001' AND
>>>> ST_Intersects(ST_Buffer(g1.Shape,-1), g2.Shape))
>>>>
>>>> THIS IS THE EXPLODED 6 FEATURES CODE: 5sec 209 rows
>>>> SELECT DISTINCT g1.objectid As taxpar_id, g1.tax_parcel_num As
>>>> parcel_number, g2.objectid As fw_id, g2.wdfw_phs, g2.wdfw_occur_pt,
>>>> g2.wdfw_haulout, g2.pc_for_fish, g2.wdfw_fish_dist, g2.pc_oaks,
>>>> g2.pc_salmon, g2.wdfw_occur_pl, g2.doh_sf, g2.wdfw_owl, g2.pc_eelgrass,
>>>> g2.pc_hydro, g2.wdfw_sasi
>>>>        FROM loader.multi_parcel As g1,
>>>> loader.potential_fw_habitat_cons_areas_pg
>>>> As g2
>>>>    WHERE (g1.tax_parcel_num = '0618161001' AND
>>>> ST_Intersects(ST_Buffer(g1.Shape,-1), g2.Shape))
>>>>
>>>> --
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>>>>
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>>
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