topic Re: Cursor Performance against Layer Selections in Python Questions

Cursor Performance against Layer Selections

tcrammond — Fri, 16 Aug 2024 16:49:45 GMT

I've been passing the results of selections against layers directly to the arcpy.da.UpdateCursor, and noticed that the performance is terrible. I love the convenience of not deriving some whacky SQL to tell the cursor exactly what I want to update...but at this point, the juice ain't worth the squeeze.

Any tips on making this work? The process is usually something like

selected_stuff = arcpy.GetParameter('selection') # feature layer input with a selection applied metrics = {id: metric for id, metric in results} # parse through some table of results to get the stuff I wan to update with arcpy.da.UpdateCursor( selected_stuff, field_names=['id', 'metric'], ) as i_cursor: for row in i_cursor: metric = metrics.get(row[0]) if metric and metric != row[1]: row[1] = metric i_cursor.updateRow(row)

Re: Cursor Performance against Layer Selections

AlfredBaldenweck — Fri, 16 Aug 2024 17:14:55 GMT

I haven't run into this issue myself, but you could try something like:

selected_stuff = arcpy.GetParameter('selection') # feature layer input with a selection applied actualFC = selected_stuff.dataSource selSet = selected_stuff.getSelectionSet() # get set of OIDs of selected feature sql = f"OBJECTID IN ({', '.join([str(i) for i in selSet])})" metrics = {id: metric for id, metric in results} # parse through some table of results to get the stuff I want to update with arcpy.da.UpdateCursor( actualFC, field_names=['id', 'metric'], where_clause = sql ) as i_cursor: for row in i_cursor: metric = metrics.get(row[0]) if metric and metric != row[1]: row[1] = metric i_cursor.updateRow(row)

Basically, run the cursor on the actual table based on what you have selected, rather than on the layer.