Tag: Database Optimization

GeoServer, GeoWebCache

GeoServer and efficient delivery of raster data (image pyramid layer)

One thing I’ve learned in the last few years is that there is no theoretical reason why (properly indexed and summarized) data cannot be displayed at all scales as quickly as at any scale. This is the principle at work behind the extraordinary efficiencies of delivering data and imagery through a slippy map interface like Google, Bing, and OpenLayers as well as efficient thick client … Continue reading GeoServer and efficient delivery of raster data (image pyramid layer)

Unknown's avatarsmathermather5 Comments
Database, PostGIS, SQL

pgagent — when triggers are too much

This will be one of my shorter posts. pgadmin III allows for the development of scheduled tasks that run on your PostgreSQL database. As my PostGIS triggers have gotten more complicated, and since they run per transaction to keep ACID compliance, a big mess can be made by just updating a dataset (this is what vacuum is good for), and the time for inserts can … Continue reading pgagent — when triggers are too much

Unknown's avatarsmathermather1 Comment
Database, PostGIS, SQL

Cost of nearest neighbor search depending on distance

A quick review of costs to search with increasing distances.  Reference this original post for the code being run. SELECT DISTINCT ON(g1.gid)  g1.gid as gid, g2.gid as gid_ground, g1.x as x, g1.y as y, g2.z as z, g1.z – g2.z as height, g1.the_geom as geometry FROM veg As g1, ground As g2    WHERE g1.gid <> g2.gid AND ST_DWithin(g1.the_geom, g2.the_geom, 3.5)    ORDER BY g1.gid, … Continue reading Cost of nearest neighbor search depending on distance

Unknown's avatarsmathermatherLeave a comment
Database, Database Optimization, PostGIS, SQL

Further optimization of the PostGIS LiDAR Vegetation Height Query

There’s much to be said for knowing your data in order to best optimize the analysis of it.  Beyond all other bits of cleverness, having a functional understanding of your problem is the first step toward conceiving an intelligent and efficient solution. One thing that I didn’t do two posts ago was to spend any time deciding how far out the search for nearby points … Continue reading Further optimization of the PostGIS LiDAR Vegetation Height Query

Unknown's avatarsmathermather1 Comment
Database, Database Optimization, PostGIS, SQL

Trigger Speeeeed, or triggers and data maintenance in PostGIS

I have completed 4 out of 6 of my triggers for maintaining boundary data in PostGIS.  This is a follow-up to this post.  If you haven’t read my PostGIS trigger post, follow this link and come back.  I’ll wait.  Go on. Back?  OK.  So I’ve implemented my property boundary triggers.  I need about 6-7 different versions of our boundary for cartographic reasons– some which are … Continue reading Trigger Speeeeed, or triggers and data maintenance in PostGIS

Unknown's avatarsmathermather3 Comments
Database, Database Optimization, PostGIS, SQL

PostGIS and LiDAR, the saga completes?

I have to thank this post for the code that follows http://postgis.refractions.net/pipermail/postgis-users/2009-June/023660.html: I’ve been putting at this nearest neighbor for points problem for a few months now, never dedicating enough time to think in through, nor expending enough energy to be really great at SQL, let alone how it can be applied in spatial operations with an OGC compliant database like PostGIS.  But here’s my … Continue reading PostGIS and LiDAR, the saga completes?

Unknown's avatarsmathermather2 Comments
Database, Database Optimization, PostGIS, SQL

Optimizing PostGIS Geometry Functions– Mmm. Donut.

Well, how can I PostGIS without referring back to BostonGIS.  One day I’ll know… .  But first, the Simpsons:  “Mmm… … Donut.” A while back I read Regina Obe’s BostonGIS post on “Map Dicing,” essentially using a grid to dice up an existing dataset to a small granularity in order to take full advantage of spatial indexing, etc..  The post really intrigued me, and is … Continue reading Optimizing PostGIS Geometry Functions– Mmm. Donut.

Unknown's avatarsmathermather1 Comment
Database, Database Optimization, PostGIS, SQL

Contour data and table management in PostGIS

My contour dataset is almost ready to go live.  Just a few more tweaks.  I was manipulating it in the public schema.  I really want it in my base map schema “base”. Want to change schemas on a table in Postgre? No problem: ALTER TABLE public.cuy_contours_2_clip SET SCHEMA base; Rename a table? No problem: ALTER TABLE base.cuy_contours_2_clip RENAME TO base.cuy_contours_2; Save space by not storing … Continue reading Contour data and table management in PostGIS

Unknown's avatarsmathermather1 Comment
Database, Database Optimization, PostGIS, SQL

PostGIS and LiDAR– oops!

I won’t offer much prelude.  Read this post, and this post first… . Inadvertently I demonstrated the value of spatial indices, i.e. I meant to use them and didn’t.  In attempting to sort my tables by their spatial index I got the following errors: ALTER TABLE lidar_ground CLUSTER ON lidar_ground_the_geom_idx; ERROR:  “lidar_ground_the_geom_idx” is not an index for table “lidar_ground” ALTER TABLE lidar_veg CLUSTER ON lidar_veg_the_geom_idx; … Continue reading PostGIS and LiDAR– oops!

Unknown's avatarsmathermatherLeave a comment