[postgis-users] Advantages and disadvantages of storing raster in PostGIS raster

[Bborie Park]

You've hit the nail on the head.  ST_Union is way too slow in its
current form.  Once I rewrite the map algebra, performance should
improve dramatically.

You can do analysis on rasters now, just in a round-about fashion.  It
also depends on what you need to do.  If you're doing something pixel by
pixel independently, that can be done now.  If you need something that
requires a neighborhood (especially across tiles), there is nothing
sufficient in place.

Raster from the file system are always faster for raw access.  The
difference is when you need to do something with the raster.  If the
raster is on the file system, you use a 3rd party application or write
your own.  If in the database, you use SQL provided by whatever client
you want.  This is similar to discussions of geometries in the database
versus in shapefiles or other file-based containers.

I currently have ~300 GB of rasters loaded into PostGIS raster (in-db)
and performance is more than adequate for researchers and web end-users.
 I need to do some testing with out-db rasters to see what the
performance is like.

-bborie

On 08/23/2012 01:12 PM, Jakub Hettler wrote:
> That was one of my questions, how to make analasys on tiled rasters? Is
> that possible or not, I tried to make ST_Union on 200 tiles and I stopped
> it after a few minutes :)
> 
> I am testing raster automatic publication of OGC services through PostGIS
> raster and image mosaic JDBC plugin and Java a I am quiet satisfied, but I
> have only small rasters (max 30 Mb), I expected that it will be really slow
> (reading raster from database, merging together and visualize them), but I
> am quite surprised.
> 
> But I expect that the same rasters will be faster from file system.
> 
> Thanks
> 
> Jakub
> 
> 2012/8/23 Bborie Park <bkpark at ucdavis.edu>
> 
>> For my work, PostGIS raster provides a standardized method to store,
>> manage and query various datasets, specifically longitudinal climate
>> data and DEM for California.  This permits my end-users (researchers and
>> various decision support software) to use the SQL knowledge they already
>> know to get the data that they're looking for without needing additional
>> software (ENVI, ERDAS Imagine, ArcGIS).
>>
>> The biggest limitation to PostGIS raster in 2.0 (and trunk) is that
>> there isn't advanced map algebra support (needed for fast unioning and
>> model output).  I hope to start working developing that support in the
>> next week or two... as I need it for my work.
>>
>> -bborie
>>
>> On 08/23/2012 11:34 AM, Jakub Hettler wrote:
>>> Hi,
>>> just a simple question, I try to find some work on this issue, but
>> nothing
>>> found.
>>>
>>> Could somebody provide some information?
>>>
>>> Thanks a lot
>>>
>>> Jakub
>>>
>>>
>>>
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>>
>> --
>> Bborie Park
>> Programmer
>> Center for Vectorborne Diseases
>> UC Davis
>> 530-752-8380
>> bkpark at ucdavis.edu
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>>
> 
> 
> 
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-- 
Bborie Park
Programmer
Center for Vectorborne Diseases
UC Davis
530-752-8380
bkpark at ucdavis.edu