| Re: [udig-devel] spatial query plug-in |
Murray Richardson wrote:
Hello,I am new to uDIG and eclipse development, but have experience with Java programming and PostgreSQL. I am trying to teach myself some basics on programming with uDIG and postgreSQL and am looking for a bit of direction on a plug-in I would like to try. The documentation has been helpful so far but I could use some specific direction.
Cool.
Essentially I have massive point and line data layers stored in a postgreSQL database that are too big to display within uDIG in their entirety (e.g. 37 million points).Well that sounds like it would take a bit of time to draw (uDig will not die, but you you would be in for a wait). You may want to construct a polygon layer with a count of how many points are recorded in each polygon. Use that layer for quick navigation until you get "close" enough to display the real thing quickly.
Instead I would like to make a tool (modal I think) that takes a bounding box drawn with the mouse, and spatially intersects this box with the stored postGIS layer, returning only the relevant part of that layer. Although the spatial queries might take a while (e.g they sometimes take 30min - 1 hour even with geometry indexing), this would greatly facilitate extracting relevant portions of the data since I only require small portions of it at any one time.You may just be able to use "selection", turn off your layer (do it is not drawn), select the area you are interested in, and export he result as a shape file.
Can I implement this idea as a modal tool and use JDBC to connect to and query the massive postGIS layer?For sure, the existing tool tutorial shows you how to draw a line. You can modify this example to collect the two corners of your bounding box. A similar trick was used by the DivaGIS project to define a "selected grid"; and then a bunch of operations were defined taking the selected grid into account. Indeed their problem is similar to yours - as their point layer represents data samples. The DivaGIS source code is in the community section.
For example after the bounding box is drawn, the tool prompts to select from a list of postGIS layers?You can either prompt (modal dialog), or open a view for your list of postGIS layers.
It concerns me that your query takes 30 mins, any chance you can perform the analysis you need on the database side using SQL? Or are you trying for an export ...
Alternatively, should I implement this as an operation that uses a existing (bounding box or polygon) layer? Any advice to point me in the right direction on this would be greatly appreciated.Thanks, Murray Richardson udig-devel-request@xxxxxxxxxxxxxxxxxxxxx wrote:Mailing list subscription confirmation notice for mailing list udig-devel We have received a request from e96:1200:a00:0:cce1:f7bf:1860:6f09 for subscription of your email address, "murray.richardson@xxxxxxxxxxx", to the udig-devel@xxxxxxxxxxxxxxxxxxxxx mailing list. To confirm that you want to be added to this mailing list, simply reply to this message, keeping the Subject: header intact. Or visit this web page:http://lists.refractions.net/mailman/confirm/udig-devel/8ceafa8fe94ba3ebb9a0271237d061c9de2cd239Or include the following line -- and only the following line -- in a message to udig-devel-request@xxxxxxxxxxxxxxxxxxxxx: confirm 8ceafa8fe94ba3ebb9a0271237d061c9de2cd239 Note that simply sending a `reply' to this message should work from most mail readers, since that usually leaves the Subject: line in the right form (additional "Re:" text in the Subject: is okay). If you do not wish to be subscribed to this list, please simply disregard this message. If you think you are being maliciously subscribed to the list, or have any other questions, send them to udig-devel-owner@xxxxxxxxxxxxxxxxxxxxx._______________________________________________ User-friendly Desktop Internet GIS (uDig) http://udig.refractions.net http://lists.refractions.net/mailman/listinfo/udig-devel