[postgis-users] Triggers and Spatial

[Paul Ramsey]

Indeed it does apply, and should be an often used arrow in the spatial 
database designers quiver. For example, that table full of street 
addresses that you want to be spatial? Add a POINT column to it, and add 
a trigger on insert and update that runs a geocoding process and 
populates the column. Then procede as normal.

Or, say you have a parcel fabric and you want titles to have notations 
about rights of way that overlap. Throw away that mylar! Capture your 
rights-of-way spatially, and add a trigger to your RoW table that does 
an overlay with parcels on insert and update, and adds the notations 
automatically. Heck, then add a trigger to the parcel table that 
populates a mailing list table of people who need to be notified about 
new encumberances.

It goes on and on... ;) Managing spatial data should not be a pain, it 
should be a largely automated addition to your normal workflow. The only 
addition should be that you capture the spatial component of your data 
as soon as possible (preferably the same time you capture any 
information at all) and get it into the system. Once there, it can flow 
unimpeded through the rest of your processes and add value at almost 
every turn.

P.

chodgson at refractions.net wrote:
> I've actually never written a trigger, so the manual will be able to tell you 
> how to do it better than me... I just know the concept and thought it would 
> apply.
> 
> Chris
> 
> Quoting Tyler Mitchell <TMitchell at lignum.com>:
> 
> 
>>>It would be possible to put a trigger on your table that took the
>>>float columns
>>>and created a point or line geometry out of them, and updated a
>>>geometry column
>>>in your database, every time a row was inserted or updated. Then
>>
>>youcould do
>>
>>>all the geometric operations you want, even spatial indexing, without
>>
>>really
>>
>>>having to worry about the non-standard sql portion of the database
>>>(other than
>>>writing the initial trigger function).
>>
>>Nice suggestion Chris! An often overlooked feature of the database.  Got
>>any examples handy?  I'm using views like this when I really should use a
>>trigger.


-- 
       __
      /
      | Paul Ramsey
      | Refractions Research
      | Email: pramsey at refractions.net
      | Phone: (250) 885-0632
      \_