PostgreSQL Hack

Feb 21, 2019 | GDAL, postgis, QGIS, Tennessee

Many of you will look and go “OMG – Randy has a new hack for a database”. No – Randy is a hack at databases.

So about 4 or 5 years ago I was dropped into the idea of databases. I was working a job several thousands miles to the south and life was easier with a database as opposed to flat files. Up until that point I had flirted with databases and taken some online courses. I would make small databases but it wasn’t something I had to deal with day to day. I did deal with it indirectly – because at the time my employer was running ArcSDE on top of Oracle – BUT – as a lowly employee I wasn’t allowed to do much with it. That was the job of the admins. I made ESRI File based Geodatabases and was quite happy. Every now and then I’d even make Microsoft Access based ones.

So flash forward to this last year and I’ve been up to my neck in databases. A lot of you will shrug. You do amazing things with PostgreSQL and SQL server and it’s not that big of a deal. Last year I did my third big migration of flat Geo files into PostgreSQL/PostGIS. It was a fairly simple thing to do: QGIS, PostGIS, and I loaded Geoserver (but we still haven’t used it – I’m confident we will).

The client moved from a “ArcView/File based Geodatabse” environment to a multiuser database environment. They are a 911 and it’s a small county. They went from 1 person being able to work to 3 people working and viewing the data. I think currently they have 4 people adding data and updating data now. That’s a win.

My god the dots

What wasn’t a win was my moving of data into the database. File based Geodatabases don’t have a primary key. Maybe there is some way to deal with that these days – I don’t know. So they were using an extension called Attribute Assistant to deal with unique columns and sequences in ArcMap. I loaded the data and didn’t pay enough attention to what was happening.

To make a short story longer – I mucked up the unique column that the data had. I didn’t know it had to be assigned then never change – as explained “it just needs to be unique”. When I loaded it the Primary key and the Unique ID were off. Primary key was 4 and ID was 5. Look there is a primary key of 10 and a ID of 247. The unique ID had nothing to do with the county data – but everything with the state 911 database. So I calc’d the ID off the Primary key and that’s when things went stupid. So what magical GIS thing did I do? I didn’t.

I made a new index column.

update hc911.addresspoints set index = right(oirid, -6)::int;

Which ripped the number off the unique column and assigned it to a new field. I built a new sequence with a new incrementing value. I messed that up. I ended up redefining a new primary key. Fixed. No GIS knowledge applied – just databases.

How do you know you are tired? This is how!

Which – not a huge deal but for me a learning experience. I need to spend one day talking to the client and making out a path way before we migrate. Migrating data took 2 hours. Institutional knowledge probably would have taken 8 hours. The next one won’t have this problem. You’re going to have to talk to me a lot about your data and process. Way more than you want and that’s fine – we just need to talk.

Data is everything. To make everyone happy I set up a few cron jobs to dump data into Geopackage and Shapefiles using OGR. They’ve been quietly chugging along for 6 months now doing their work with no applause or fanfare. More people in the office are slowly going “hey you mean I can use QGIS to connect to the database? I can see the data?”.

I can say this whole move minus the ID hiccup has been a huge win for the organization. I was just lucky enough to be the guy to do it.

So if you’re an organization struggling with your commercial system – why not take a look at this side of the fence. We’re a lot of fun. If you’re wondering “Hey what should I learn these days” – I invite you to dive into PostgreSQL/PostGIS.

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