[postgis-users] Querying Multiple Rasters

Jayson Gallardo jaysontrades at gmail.com
Tue Jul 30 09:25:38 PDT 2013 

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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