[postgis-users] Querying Multiple Rasters

Jayson Gallardo jaysontrades at gmail.com
Tue Jul 30 09:35:11 PDT 2013


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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