I am trying to optimize a script that uses addJoin_management. To do this efficiently, I am attempting to add an attribute index on the join table. I am getting a generic error when i do this though.

arcgisscripting.ExecuteError: ERROR 999999: Error executing function. Failed to execute (AddIndex).

My code does an intersect, dissolve, calculate acres, join and then re-calculate the acres column to the target table.

EDIT: See below for my solution.

  • 1
    I have been doing something very similar recently in model builder and can confirm that in_memory datasets do not support indices. I ended up using the %ScratchGDB% workspace in model builder
    – Hornbydd
    Commented Dec 23, 2015 at 17:35
  • 1
    It's strange, I had the same problem where I needed to add an index to both layers I am joining, it is only one of them that fail though with an error along the lines of 'index exists'. While the other runs every time. Also, I write the line differently, in your case arcpy.AddIndex_management(dissolved,"FID_Parcels_2013", "ID", 1, 1) rather than spelling out the 'unique' and 'ascending' options. Does "ID" stands for your index name? I run my data off disk so like @Hornbydd said it might be an in memory issue
    – yanes
    Commented Dec 23, 2015 at 17:50
  • Yes ID is the index name. I want to avoid writing anything to disk but it looks like I may have to in order to perform the addIndex operation.
    – its30
    Commented Dec 23, 2015 at 19:08
  • did you try the, the other code? with 1,1 rather than spelling out the options? because I'd think it would give more than a generic 9999 error, if it is not a syntax issue...
    – yanes
    Commented Dec 23, 2015 at 21:57
  • I didnt get a chance to try that out. Ill give it a shot when i return to work monday. For now i am just writing the 'dissolved' to disk and deleting after I have completed all the other steps.
    – its30
    Commented Dec 24, 2015 at 0:36

1 Answer 1


My Solution: I was never able to get the in_memory variable working with AddIndex_management. I ended up using the arcpy.env.scratchGDB.

# in_memory variables do not work with AddIndex Management
# dissolve_out = "in_memory" + "\\" + "mem_dissolved" 

# The solution:
dissolve_out =  os.path.join(arcpy.env.scratchGDB, "scratch_dissolve_out")

arcpy.AddIndex_management(dissolve_out ,"FID_Parcels_2013", "ID", "UNIQUE", "ASCENDING")

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