topic Re: FeatureLayer : Without ObjectId Field? in ArcGIS JavaScript Maps SDK Questions

FeatureLayer : Without ObjectId Field?

__Rich_ — Mon, 02 Apr 2012 12:22:29 GMT

Hi,

I've got a layer within an AGS service that returns a load of point features based on dynamically changing data held in a non-spatial database via an ODBC connection, I'd like to connect a FeatureLayer to the service but it only renders a single feature in the map.

I can see from some investigations that the ESRI JavaScript relies (very heavily) on there being one field in the data that can be used as the 'ObjectIdField' to uniquely identify rows, there isn't an appropriate field in my data and I don't really want to arbitrarily generate something for these data.

Anyone found a way around this restriction?

Thanks.

Re: FeatureLayer : Without ObjectId Field?

ChadWilcomb — Mon, 02 Apr 2012 12:42:34 GMT

Try using a Query Layer to load the data into your MXD. Go to File -> Add Data -> Add Query Layer, connect to your database and write a query (or double-click on a table to Select *). Click "Show Advanced Options", then select one or more fields to create a unique identifier.

Re: FeatureLayer : Without ObjectId Field?

__Rich_ — Mon, 02 Apr 2012 13:17:03 GMT

Try using a Query Layer to load the data into your MXD. Go to File -> Add Data -> Add Query Layer, connect to your database and write a query (or double-click on a table to Select *). Click "Show Advanced Options", then select one or more fields to create a unique identifier.

Thanks for the response, Chad - looks like it might work, I don't suppose you know where it stores the connection info? I'm going to need to move the mxd to an AGS machine on a different network that hasn't got ArcDesktop installed so being able to re-map connections is a must, in the past I've achieved this using ODBC DSNs etc.

edit: found the .qcf file....it doesn't look portable!

Re: FeatureLayer : Without ObjectId Field?

PaulBushore — Mon, 02 Apr 2012 13:25:47 GMT

ArcCatalog connection information is usually kept in the hidden appdata folder for that user. With 10, you can now copy and paste the database connection item in the ArcCatalog data tree and paste it where you want it.

Re: FeatureLayer : Without ObjectId Field?

__Rich_ — Mon, 02 Apr 2012 13:37:40 GMT

ArcCatalog connection information is usually kept in the hidden appdata folder for that user. With 10, you can now copy and paste the database connection item in the ArcCatalog data tree and paste it where you want it.

Thanks, Paul.

Yep, I've made use of that with .odc files in the past but it would appear that a connection created via "Add Query Layer" is a different kettle of fish, seems to have placed the connection information in a .qcf file which is presumably referenced by the mxd and cannot be moved. Even if I could move it I'd have to go around naming all database host machines with the same name etc. or purchase a bucketload of ArcDesktop licenses for each AGS machine on each network!

Re: FeatureLayer : Without ObjectId Field?

__Rich_ — Mon, 02 Apr 2012 14:03:48 GMT

Progress...maybe.

Created as per the 'wizard' then remapped data sources to .odc connection which in turn uses an ODBC DSN, deleted .qcf file and the data still display...so dependency on .qcf removed....I think.

So:

1. ODBC DSN can be created anywhere, to point wherever I want
2. .odc file can be created and copied to known location and references ODBC connection by its DSN
3. mxd can be copied to known location and references .odc at known location thus can be connected to whatever server I want

Assuming, that's all valid, it can work...just a bit (very, very) convoluted.

Next problem is that the resultant layer won't accept simple definition queries e.g. Year(mydatetimefield) = 2012 "Failed to parse the where clause"!

I suppose I'll have to write all the queries in step 1 i.e. when adding the query layer!

Blimey.

Re: FeatureLayer : Without ObjectId Field?

derekswingley1 — Mon, 02 Apr 2012 14:21:47 GMT

What's the reasoning behind not wanting to add an object id field client side?

Re: FeatureLayer : Without ObjectId Field?

__Rich_ — Mon, 02 Apr 2012 14:26:33 GMT

Actually, scratch all that.

The step "Add Query Layer" that asks you to select the unique identifier fields is a problem, actually it's the original problem.

There are no fields in this dataset that consitute a unique identifier, it's the nature of the data. If I choose a field or a composite of fields then effectively I'll be filtering out data because ArcDesktop will assume they're dusplicate records because they have matching 'key' values.

I just want the software to plot the points in the database, all of them. AGS renders them all in the images it produces and it also provides them in the JSON is returns, it's just the client-side FeatureLayer code that lets the side down and unfortunately I need other parts of its functionality.

Thanks for the responses but it looks like this is a dead end.

Re: FeatureLayer : Without ObjectId Field?

ChadWilcomb — Mon, 02 Apr 2012 14:30:00 GMT

What's the reasoning behind not wanting to add an object id field client side?

Derek, do you have any samples on how to do this?

Re: FeatureLayer : Without ObjectId Field?

derekswingley1 — Fri, 10 Dec 2021 20:09:24 GMT

It's simple to add a unique field to your data client side. You can do it with three lines of code, something like:

dojo.forEach(data, function(d, idx) {
  d.attributes.oid = idx;
});

And in your feature collection, make sure your field named oid (or whatever you choose to name it) has a type of esriFieldTypeOID.

Re: FeatureLayer : Without ObjectId Field?

__Rich_ — Mon, 02 Apr 2012 14:33:27 GMT

What's the reasoning behind not wanting to add an object id field client side?

Hi Derek,

Where would I add it?

Would I need to intercept the query response and append the list of fields etc?

Thanks,

Rich

Re: FeatureLayer : Without ObjectId Field?

derekswingley1 — Mon, 02 Apr 2012 14:34:55 GMT

Derek, do you have any samples on how to do this?

Sorry, no samples to show manually populating an object ID.

Rather than populating a unique ID yourself, an alternative is to use applyEdits to push your data into the feature layer. This is what the feature layer from feature collection sample does with data returned from flickr that does not have a unique identifier.

Re: FeatureLayer : Without ObjectId Field?

__Rich_ — Fri, 10 Dec 2021 20:09:27 GMT

It's simple to add a unique field to your data client side. You can do it with three lines of code, something like:
dojo.forEach(data, function(d, idx) {
  d.attributes.oid = idx;
});
And in your feature collection, make sure your field named oid (or whatever you choose to name it) has a type of esriFieldTypeOID.

Where would that forEach sit?

Re: FeatureLayer : Without ObjectId Field?

derekswingley1 — Mon, 02 Apr 2012 14:36:50 GMT

The forEach would run after you've retrieved your data but before you create your feature layer.

Since it sounds like you're not using a layer from a map service, I assumed your creating a feature layer from a feature collection. Are you using a feature collection?

Re: FeatureLayer : Without ObjectId Field?

__Rich_ — Mon, 02 Apr 2012 14:38:31 GMT

The forEach would run after you've retrieved your data but before you create your feature layer.

Since it sounds like you're not using a layer from a map service, I assumed your creating a feature layer from a feature collection. Are you using a feature collection?

Nope, the data are from an AGS map service...which is why I'm surprised that this does not 'just work' out of the box.

Re: FeatureLayer : Without ObjectId Field?

derekswingley1 — Mon, 02 Apr 2012 14:43:08 GMT

Nope, the data are from an AGS map service...which is why I'm surprised that this does not 'just work' out of the box.

In that case, it's best to add your unique ID on the server. Does the layer have a primary key? Are you able to make selections against it in ArcMap?

Re: FeatureLayer : Without ObjectId Field?

__Rich_ — Mon, 02 Apr 2012 14:47:32 GMT

In that case, it's best to add your unique ID on the server. Does the layer have a primary key? Are you able to make selections against it in ArcMap?

I can query against the source in ArcMap, specifically I'm doing some DateDiff stuff to limit the results.

The nature of the data means it would be dangerous to choose a key from actual data fields as it would remove records that in reality are not duplicates.

Re: FeatureLayer : Without ObjectId Field?

derekswingley1 — Mon, 02 Apr 2012 14:52:19 GMT

I can query against the source in ArcMap, specifically I'm doing some DateDiff stuff to limit the results.

Hmm, I'm surprised to hear that. Can you talk a bit more about your data source? How is the data added to ArcMap? What's the data store being used for this data?

The nature of the data means it would be dangerous to choose a key from actual data fields as it would remove records that in reality are not duplicates.

In that case, can you have your database auto-populate a unique field? All the main RDBMS's have this capability but you would probably have to create a new table and reload your data.

Re: FeatureLayer : Without ObjectId Field?

__Rich_ — Mon, 02 Apr 2012 15:09:44 GMT

Will post more info tomorrow, bit too much to type on a phone!

Re: FeatureLayer : Without ObjectId Field?

__Rich_ — Fri, 10 Dec 2021 20:09:30 GMT

Hmm, I'm surprised to hear that. Can you talk a bit more about your data source? How is the data added to ArcMap? What's the data store being used for this data?

Me too.

The data source is an XY Event Source, underlying that is a .odc file (created with ArcCatalog) that uses an ODBC DSN which in turn uses the SQL Server Native Client library to connect to a SQL Server instance.

But you don't need all that to reproduce the scenario, you could get to this point using a simple CSV file like:

long,lat,message
1,1,hello world
2,2,hello again world

In that case, can you have your database auto-populate a unique field? All the main RDBMS's have this capability but you would probably have to create a new table and reload your data.

Creating a surrogate key where it's appropriate for the data is acceptable, but in this case it'd be a hack, the (identity) value would have no 'meaning' to the data values etc.

The underlying issue is that although the FeatureLayer JS knows that the data has no OID value (and logs this fact to the console) it continues to try and use it as a key to the data, I can point you towards the method(s) in the class where this causes issues if that helps?

I understand the need for a key to identify data if, for example, I was providing some editing of persistable features, but in this case all I want to do is display the features in the map, just like the ArcGISDynamicServiceLayer would, but because I need some client-side functionality not available with an image-based layer type the FeatureLayer appeared to be the best choice....apart from this (rather severe) issue!