[postgis-users] Querying Multiple Rasters

Bborie Park dustymugs at gmail.com
Tue Jul 30 09:39:39 PDT 2013 

The quick and dirty approach is to have a query before that query that
transforms the WKT.

Something like "SELECT ST_AsEWKT(ST_Transform(...))"

-bborie


On Tue, Jul 30, 2013 at 9:35 AM, Jayson Gallardo <jaysontrades at gmail.com>wrote:

> I suppose I could do that in my script. How should I go about that? My
> process is as follows:
>
>    - User selects area of interest on a map (openlayers)
>    - User clicks submit, and python script is called with the WKT passed
>    as an argument
>    - Python script queries the database, which then outputs the raster
>    - Raster is processed through a library
>    - Processed raster is displayed as an overlay on the map
>
>
>
> On Tue, Jul 30, 2013 at 11:31 AM, Bborie Park <dustymugs at gmail.com> wrote:
>
>> Are you able to transform the wkt before passing it to the sql?
>> Partitioning only works on constant values, not values that need
>> processing, e.g. ST_Transform(ST_GeomFromText(\'%s\',%i),%i)).
>>
>> -bborie
>>
>>
>> On Tue, Jul 30, 2013 at 9:25 AM, Jayson Gallardo <jaysontrades at gmail.com>wrote:
>>
>>> Here's the constraints:
>>>   CONSTRAINT dem_elevation_n33w092_pkey PRIMARY KEY (rid ),
>>>   CONSTRAINT enforce_height_rast CHECK (st_height(rast) = 100),
>>>   CONSTRAINT enforce_max_extent_rast CHECK
>>> (st_coveredby(st_convexhull(rast), '*...truncated...*'::geometry)),
>>>   CONSTRAINT enforce_num_bands_rast CHECK (st_numbands(rast) = 1),
>>>   CONSTRAINT enforce_out_db_rast CHECK (_raster_constraint_out_db(rast)
>>> = '{f}'::boolean[]),
>>>   CONSTRAINT enforce_pixel_types_rast CHECK
>>> (_raster_constraint_pixel_types(rast) = '{32BF}'::text[]),
>>>   CONSTRAINT enforce_same_alignment_rast CHECK (st_samealignment(rast, '
>>> *...truncated...*'::raster)),
>>>   CONSTRAINT enforce_scalex_rast CHECK (st_scalex(rast)::numeric(16,10)
>>> = 0.000092592592593::numeric(16,10)),
>>>   CONSTRAINT enforce_scaley_rast CHECK (st_scaley(rast)::numeric(16,10)
>>> = (-0.000092592592593)::numeric(16,10)),
>>>   CONSTRAINT enforce_srid_rast CHECK (st_srid(rast) = 4269),
>>>   CONSTRAINT enforce_width_rast CHECK (st_width(rast) = 100)
>>>
>>> and my python script:
>>>
>>> wkt = sys.argv[1]  # Polygon shape in WKT format
>>> raster_type = 'GTiff'
>>> table_name = 'dem_elevation'
>>> map_srs = 900913
>>> table_srs = 4269
>>> sql_text = 'SELECT ST_AsGDALRaster(ST_CLIP(ST_Union(rast),
>>> ST_GeomFromText(\'%s\',%i)),\'%s\') FROM "%s" WHERE ST_Intersects(rast,
>>> ST_Transform(ST_GeomFromText(\'%s\',%i),%i))' % (wkt, map_srs,
>>> raster_type, table_name, wkt, map_srs, table_srs)
>>>
>>>
>>>
>>> On Tue, Jul 30, 2013 at 11:12 AM, Bborie Park <dustymugs at gmail.com>wrote:
>>>
>>>> Jayson,
>>>>
>>>> Can you share one of the queries? Also, what check constraints are you
>>>> using?
>>>>
>>>> -bborie
>>>>
>>>>
>>>> On Tue, Jul 30, 2013 at 7:49 AM, Jayson Gallardo <
>>>> jaysontrades at gmail.com> wrote:
>>>>
>>>>> So, I used Explain on my SELECT statement, and whether
>>>>> constraint_exclusion is on or off, it seems to spit out the same number of
>>>>> rows in the query plan. Is there something I need to do for my table
>>>>> constraints so that it doesn't do a check on every table I have loaded?
>>>>>
>>>>>
>>>>> On Tue, Jul 30, 2013 at 9:20 AM, Jayson Gallardo <
>>>>> jaysontrades at gmail.com> wrote:
>>>>>
>>>>>> Quick follow up question to my situation... I recently loaded 3m
>>>>>> resolution NED for Iowa. I have them loaded to one table per source tile,
>>>>>> and have them inheriting from the parent table that the Arkansas NED is
>>>>>> inheriting from. Ever since, however, my database seems to be running
>>>>>> pretty slow. I've run a full vacuum on the data, and there are constraints
>>>>>> on each table.
>>>>>>
>>>>>> How can I be sure that when I query the parent database that it's not
>>>>>> querying every single table?
>>>>>>
>>>>>>
>>>>>> On Tue, Jul 23, 2013 at 3:14 PM, Bborie Park <dustymugs at gmail.com>wrote:
>>>>>>
>>>>>>> I'm just glad to help. Feel free to post your experience, feedback,
>>>>>>> issues and/or wishes on the mailing-list.
>>>>>>>
>>>>>>> -bborie
>>>>>>>
>>>>>>>
>>>>>>> On Tue, Jul 23, 2013 at 1:10 PM, Jayson Gallardo <
>>>>>>> jaysontrades at gmail.com> wrote:
>>>>>>>
>>>>>>>> Oh, okay. Yeah you're right about it taking time. I wrote a python
>>>>>>>> script to generate the raster2pgsql call with the appropriate table name,
>>>>>>>> so I can just let it run while I do other things. I really appreciate your
>>>>>>>> help on this. I googled your name and I see you're a pretty busy person, so
>>>>>>>> I'm glad you're taking the time to answer my questions.
>>>>>>>>
>>>>>>>>
>>>>>>>> On Tue, Jul 23, 2013 at 3:05 PM, Bborie Park <dustymugs at gmail.com>wrote:
>>>>>>>>
>>>>>>>>> No. I'm suggesting it later as it does take time and separates
>>>>>>>>> operations. Get everything imported first and then add constraints.
>>>>>>>>>
>>>>>>>>> Having said that, you can do it all at once if so desired... just
>>>>>>>>> preference depending on volume of import data.
>>>>>>>>>
>>>>>>>>> -bborie
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Tue, Jul 23, 2013 at 1:02 PM, Jayson Gallardo <
>>>>>>>>> jaysontrades at gmail.com> wrote:
>>>>>>>>>
>>>>>>>>>> Okay, is there a specific reason why? As your link states: "
>>>>>>>>>> raster2pgsql loader uses this function to register raster
>>>>>>>>>> tables". Are you saying I should specify constraints that will be similar
>>>>>>>>>> across all tables?
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Tue, Jul 23, 2013 at 2:53 PM, Bborie Park <dustymugs at gmail.com
>>>>>>>>>> > wrote:
>>>>>>>>>>
>>>>>>>>>>> I'd suggest adding constraints after the fact through SQL
>>>>>>>>>>> instead of letting raster2pgsql do it.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> http://www.postgis.net/docs/manual-2.0/RT_AddRasterConstraints.html
>>>>>>>>>>>
>>>>>>>>>>> -bborie
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On Tue, Jul 23, 2013 at 12:51 PM, Jayson Gallardo <
>>>>>>>>>>> jaysontrades at gmail.com> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> So based on the link you provided, and what else I've gathered,
>>>>>>>>>>>> I first create a parent table:
>>>>>>>>>>>>  CREATE TABLE dem_elevation
>>>>>>>>>>>> (
>>>>>>>>>>>>   rid integer NOT NULL PRIMARY KEY
>>>>>>>>>>>>   rast raster,
>>>>>>>>>>>>
>>>>>>>>>>>> );
>>>>>>>>>>>>  Then I run raster2pgsql on all the downloaded elevation data,
>>>>>>>>>>>> sending each input tile to its own table, ie. dem_elevation_n36w091. Then
>>>>>>>>>>>> alter table to inherit from parent:
>>>>>>>>>>>> ALTER TABLE dem_elevation_n36w091 INHERIT dem_elevation;
>>>>>>>>>>>>
>>>>>>>>>>>> With raster2pgsql taking care of setting the constraints for
>>>>>>>>>>>> each table. Now, I can just query the parent table dem_elevation to get
>>>>>>>>>>>> what I need?
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> On Tue, Jul 23, 2013 at 2:33 PM, Bborie Park <
>>>>>>>>>>>> dustymugs at gmail.com> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>>> I use the USGS NED 10 meter for California with one table for
>>>>>>>>>>>>> each input raster. In the partitioned table scheme, data tables inherit
>>>>>>>>>>>>> from a template (parent) table. Queries run on the parent table access the
>>>>>>>>>>>>> inherited tables.
>>>>>>>>>>>>>
>>>>>>>>>>>>> -bborie
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Tue, Jul 23, 2013 at 11:56 AM, Jayson Gallardo <
>>>>>>>>>>>>> jaysontrades at gmail.com> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> Yes, it's usgs ned. And I initially went with one table for
>>>>>>>>>>>>>> each input tile, but I didn't know how to join (or union) them together for
>>>>>>>>>>>>>> my query.
>>>>>>>>>>>>>>  On Jul 23, 2013 1:14 PM, "Bborie Park" <dustymugs at gmail.com>
>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Can you describe your elevation dataset? Is it USGS NED? At
>>>>>>>>>>>>>>> which resolution (10 meter, 3 meter?)?
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> As for table partitioning...
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> http://www.postgresql.org/docs/9.0/static/ddl-partitioning.html
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> You'll probably partition spatially, though an easy solution
>>>>>>>>>>>>>>> is to have a table for each input raster file.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> -bborie
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On Tue, Jul 23, 2013 at 11:05 AM, Jayson Gallardo <
>>>>>>>>>>>>>>> jaysontrades at gmail.com> wrote:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Thanks for responding. Could you outline how I would go
>>>>>>>>>>>>>>>> about doing a partitioned table structure? My only concern with tile size
>>>>>>>>>>>>>>>> is processing time. Most of my queries will involve areas of less than 1
>>>>>>>>>>>>>>>> mi^2, and I would clip the data into that shape. I just don't know where to
>>>>>>>>>>>>>>>> start! There's not too many resources online/print dealing with postgis
>>>>>>>>>>>>>>>> rasters in detail.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> On Tue, Jul 23, 2013 at 12:57 PM, Bborie Park <
>>>>>>>>>>>>>>>> dustymugs at gmail.com> wrote:
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> You may not need to drop all the constraints when adding
>>>>>>>>>>>>>>>>> additional data to the table. You most likely will need to drop is the
>>>>>>>>>>>>>>>>> maximum extent constraint. Assuming the input rasters have the same scale,
>>>>>>>>>>>>>>>>> skew and SRID as that found in the table, you don't need to drop those
>>>>>>>>>>>>>>>>> corresponding constraints.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> If you're going to do the continental US at a fine
>>>>>>>>>>>>>>>>> resolution (e.g. 1 meter), you do NOT want to put all the rasters in one
>>>>>>>>>>>>>>>>> table. You'll want to use a partitioned table structure and should consider
>>>>>>>>>>>>>>>>> a bigger tile size (depending on your hardware).
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> -bborie
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> On Tue, Jul 23, 2013 at 10:43 AM, Jayson Gallardo <
>>>>>>>>>>>>>>>>> jaysontrades at gmail.com> wrote:
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> I've looked and looked, but I have not been able to find
>>>>>>>>>>>>>>>>>> an answer to my question. I have downloaded elevation data for the state of
>>>>>>>>>>>>>>>>>> Arkansas (in the form of multiple tiles), and used raster2pgsql to upload
>>>>>>>>>>>>>>>>>> it into a single table:
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> raster2pgsql -I -C -e -F -t 50x50 -l 2,4 n*/grdn*
>>>>>>>>>>>>>>>>>> public.dem_elevation | psql -U postgres -d testdb -h localhost -p 5432
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> I did this because I didn't know how to pull the data if
>>>>>>>>>>>>>>>>>> they were in separate tables. Now, however I would like to add elevation
>>>>>>>>>>>>>>>>>> data for other areas. I tried to just add it to the current table, but that
>>>>>>>>>>>>>>>>>> required dropping the constraints which for such a huge amount of data
>>>>>>>>>>>>>>>>>> seems to take a long time (I let it run for 24+ hours and it didn't
>>>>>>>>>>>>>>>>>> finish). So, my question is, if I load all my rasters as individual tables,
>>>>>>>>>>>>>>>>>> how could I run something similar to this query on them all (from a python
>>>>>>>>>>>>>>>>>> script):
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> SELECT ST_AsGDALRaster(ST_CLIP(ST_Union(rast),
>>>>>>>>>>>>>>>>>> ST_GeomFromText(WKT,900913)),'GTiff') FROM "dem_elevation" WHERE
>>>>>>>>>>>>>>>>>> ST_Intersects(rast, ST_Transform(ST_GeomFromText(WKT,900913),4269))
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> My goal, if it's not obvious, is to clip elevation data
>>>>>>>>>>>>>>>>>> and export it to a GTiff format and perform some operations on that raster
>>>>>>>>>>>>>>>>>> data. Eventually, I would like to put the whole continental US elevation
>>>>>>>>>>>>>>>>>> data into my database, so I need to be able to do so, while still being
>>>>>>>>>>>>>>>>>> able to query them based on an area of interest the user selects from a
>>>>>>>>>>>>>>>>>> map. I started working with PostGIS and Mapserver last month, so please
>>>>>>>>>>>>>>>>>> forgive my ignorance on such topics. Thanks in advance
>>>>>>>>>>>>>>>>>>
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>>>>>>>>>>>>>>>>>>
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