[postgis-users] Querying Multiple Rasters

Tue Jul 30 07:49:06 PDT 2013

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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