Other spatial database development (PostGIS)

[Alex Smith]

I'd like to preface this by acknowledging that my technical ineptitude may have been the cause of my unsuccessful attempts to write tabular data to external OLEDB databases from ArcGIS.  And I'd also like to point out that it's been a while since I tried doing so - things may have changed.  But my experiences have lead me to believe that ESRI has (or had) carefully implemented ArcGIS in a manner that prevents users from writing to external DBMS without  using ArcSDE.  We do alot of spatial processing that output and affects a considerable amount of tabular data that many other rely on and edit where necessary.  Because we're already pushing the limits of Access, I looked into other options when we started some new projects....and an affordable option, such as Postgres or MySQL.  Here's what I found
 
In the original "Exploring ArcObjects" book, published near the release of ArcGIS 8.0, states that OLEDB connections to ArcGIS are read only.  Hence, we couldn't directly output data to an external table joined to a Access based featureclass.  Sure, we can later use ADO to update the 'enterprise' database from the Access geodatabase, but that starts to get messy or becomes, to use Paul's words, a "moderately ugly hack" (why have the middle-man Geodatabase tables - like pgArc had the middle-man shapefiles).  So I tried linking in a MySQL table to via ODBC in a geodatabase .mdb file and attempted to edit that table (no spatial data) from ArcGIS - I got a message stating that linked tables cannot be written to.  DAO tables (and I'm fairly certain that ArcGIS interacts with Access databases using DAO), have a property that returns true if they are linked tables.   So it seems that the ArcGIS has code that tests this property and does not allow users to edit these tables.  I find it very
 hard to believe that this was accidental.  And I later felt naive for thinking I could somehow 'outsmart' them - ESRI's software engineers are not dumb.  Expect some resistance in attempting to circumnavigate their systems.  
 
I understand their need to protect their investment - the ArcGIS spatial editting tools (including topology and networks) and ArcSDE must have cost a lot of money to develop.  And it's good software - ESRI has earned a lot of its success.  It just sucks for those of us on a limited budget - SDE licenses on top of commercial RDBMS fees is simply unaffordable in our case.  
 
On the other hand, ESRI seems to be opening up.  But they must continue to recover their development costs somehow.  And I'd be surprised if they'd make it easy for other develop tools to compete with their systems.  Yes, being able to directly edit PostGIS data using ArcGIS-like editing tools would be huge....but I don't think that it would be easy and would probably be cost-prohibitive.  As Paul mentioned, if these things were easily and cost-effectively attainable, then it probably would have been done by now.  But then again....look how successful mapserver has become.  Just my thoughts......
 
Alex
Paul Ramsey <pramsey at REFRACTIONS.NET> wrote:
Guys, I am happy to spec this out again, but frankly I fear that most 
solutions will remain in the "moderately ugly hack" domain, ala 
PgArc. I have investigated more elegant things (oledb) but the signs 
are not promising (http://arcgisdeveloperonline.esri.com/ 
ArcGISDeveloper/ExtendingArcObjects/Ch07/AboutOLEDBProviders.htm). 
Principally, the continuing lack of an Oracle Spatial third party 
read/write extension on the market says to me that such a thing is 
just technically not possible to do attractively. If it were, someone 
would have written it by now and be making money on it. If anyone 
knows of such a thing, please do tell, it would be a good positive 
sign of possible success.

Paul

On 7-Jul-05, at 10:22 AM, Ken Lord wrote:

> Hi Mike,
>
> This is a major interest to us, we would like to see a push for 
> this as well, in fact I was just asked to contact Tyler Mitchell 
> about pgArc when I return from my holidays. Tyler! are your ears 
> burning? hehe
>
> pgArc can be found at SourceForge if you want to check it out. It 
> has some functionality with ArcGIS 8, but I haven't had it work 
> with ArcGIS 9.
>
> We are locked into personal geodatabases for some of our clients, 
> development of a fully functional ArcGIS / PostGIS connection would 
> give us a lot more flexibility too.
>
> Cheers,
> Ken Lord
> Vancouver BC
>
>
>
>
> On 7/7/05, Mike Davis wrote: Since we 
> seem to be building some momentum on the ESRI personal
> geodatabase thing, it seems like a good time to bring up the other
> database related item on our wishlist.
>
> What would be required to allow read/write to a PostGIS database from
> ArcGIS? I would love the ability to maintain our spatial data in
> multiple datbase formats (must me my irrational fear of vendor
> lock-in), but unless we can manage the data from within ArcGIS it
> isn't really a practical option for us.
>
> -Mike

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