Buffering with dissolve type: ALL for a big feature class doesnot create a single multipart feature

Question

I am using buffer tool on large complicated network (260,000 features) line shapefile to create an area shapefile. This area shapefile somehow has to be dissolved to a single multipart shapefile.

Code used:

arcpy.Buffer_analysis(featureLayer , temp2, "0.5 Feet", "FULL", "FLAT", "ALL") 
arcpy.Dissolve_management(temp2, temp3, "", "", "", "")
arcpy.MultipartToSinglepart_management(temp3, outputLayer)

Problem: The dissolve after buffer for some reason does not create a single multipart feature. It creates many multipart features that can't be dissolved with each other. I tried to dissolve it five consecutive times, it produced the same result.

Is there any way to dissolve all these features to create a single multipart feature?

Answer 1

You may be running into a geometry limitation of the shapefile format (Geoprocessing considerations for shapefile output).

You could try running the Buffer analysis to an in_memory feature class then CopyFeatures to a shapefile on disk.

arcpy.Buffer_analysis(featureLayer , r"in_memory\temp2", "0.5 Feet", "FULL", "FLAT", "ALL")
arcpy.CopyFeatures_management(r"in_memory\temp2", "Final_Output.shp")

If you hit the geometry limitation again you'll probably have to use a Dice to subset the polygons in some way or a Generalize.

Answer 2

Create an new feature class with the same spatial reference as the polygons you are trying to dissolve. Then use a search cursor to pull geometry objects. For each row in your buffer feature class, perform a union to create a single feature.

import os

arcpy.Buffer_analysis(featureLayer , temp2, "0.5 Feet", "FULL", "FLAT", "ALL") 
#get path and file name of temp3
temp3path, temp3name = os.path.split (temp3)
#create new feature class
arcpy.CreateFeatureClass_management (temp3path, temp3name, "POLYGON",
                                     spatial_reference = temp2)
#iterate buffer attributes, pull geometries
with arcpy.da.SearchCursor (temp2, "SHAPE@") as curs:
    for geom, in curs:
        try:
            #union current geom with all prior geoms
            unionGeom = geom.union (unionGeom)
        except NameError:
            #first geometry, just assign it as union geometry variable
            unionGeom = geom

#insert dissolved geometry into created feature class
with arcpy.da.InsertCursor (temp3, "SHAPE@") as curs:
    row = (lastGeom,)
    curs.insertRow (row)

...or without a new feature class, just dissolving a feature class with multiple features into a single feature:

#iterate buffers, get geometries
with arcpy.da.UpdateCursor (temp2, "SHAPE@") as curs:
    for geom, in curs:
        try:
            #union current geom with all prior geoms
            unionGeom = geom.union (unionGeom)
        except NameError:
            #first geometry, just assign it as union geometry variable
            unionGeom = geom
        #delete row
        curs.deleteRow ()

#create insert cursor
with arcpy.da.InsertCursor (temp2, "SHAPE@") as curs:
    #insert final union geometry
    curs.insertRow ((unionGeom,))