Latest Contributions by DuncanHornby

All, In a recent thread discussed here it was suggested that creating a FeatureLayer from a FeatureClass can improve the performance of arcpy. It was clear from the subsequent discussions that this was not necessarily accepted by others and I was skeptical as I have never seen any reference to this "top tip". So with time to kill I set out to test this and I am reporting my findings for others to mull over. I have 10.2 on a VISTA OS and a I ran everything in Pyscripter. On each run I reset the python interpreter window and reset the source dataset so the conditions were the same. I had stopped all other applications and did not touch the keyboard whilst the code ran. I had created a point shapefile with 1000 random points, my test code simply added a field and then calculated a constant value into this new field. The code repeated these steps 49 times. I record the start and end times so I could work out how long it took. I repeated the test 10 times for each scenario. My null hypothesis is that there is no performance difference. The two test scenarios where: Access the source dataset as a full path name, what you typically see in many examples in the ESRI help Create a FeatureLayer first and use that instead of the full path name My code for accessing the full path was: import arcpy import time print "START TIME = " + time.asctime() # Source dataset to update fc = r"C:\Scratch\TestLayer.shp" # Create a list of numbers from 1 to 50 l = range(1,50,1) for i in l:     # Create a field name and add it to dataset     name = "F_" + str(i)     print "Processing "  + name     arcpy.AddField_management(fc,name,"LONG")     # Populate field with a constant 999     arcpy.CalculateField_management(fc,name,"999","VB") print "END TIME = " + time.asctime() My code for accessing a FeatureLayer was: import arcpy import time print "START TIME = " + time.asctime() # Source dataset to update fc = r"C:\Scratch\TestLayer.shp" fl = "TestLayer" arcpy.MakeFeatureLayer_management(fc,fl) # Create a list of numbers from 1 to 50 l = range(1,50,1) for i in l:     # Create a field name and add it to dataset     name = "F_" + str(i)     print "Processing "  + name     arcpy.AddField_management(fl,name,"LONG")     # Populate field with a constant 999     arcpy.CalculateField_management(fl,name,"999","VB") print "END TIME = " + time.asctime() For the 10 test runs the mean time for running the code for: full path name was 22 seconds FeatureLayer was 19.5 seconds I did a Two-Sample T-Test in Minitab which is significant which means I reject my null hypothesis. Two-sample T for fl vs fc    N  Mean   StDev  SE Mean fl  10  19.500  0.527     0.17 fc  10  22.000  0.816     0.26 Difference = mu (fl) - mu (fc) Estimate for difference:  -2.500 95% CI for difference:  (-3.155, -1.845) T-Test of difference = 0 (vs not =): T-Value = -8.13  P-Value = 0.000  DF = 15 So for this simple scenario there was a significant difference in performance by creating a FeatureLayer first... Interesting hey? ... View more

All, Odd problem here and I have not found a solution to it. I'm using ArcGIS 10.1, VB .net and the source data is a shapefile.At some point in my tool I add a field using the IFeatureClass.AddField method and populate it with values but when I add this field it drops the spatial index on the dataset. In ArcMap if I open the Attribute table I see the * in the Shape field which suggests its still there but I know its not. Later on in my tool I test if a dataset has a spatial index, if not I add one. I test if the dataset has a spatial index with the following code: Dim pFeatureClass As IFeatureClass pFeatureClass = m_pFeatureLayer_River.FeatureClass Dim pIndexes As IIndexes Dim pEnumIndex As IEnumIndex pIndexes = pFeatureClass.Indexes pEnumIndex = pIndexes.FindIndexesByFieldName(pFeatureClass.ShapeFieldName) Dim pIndex As IIndex pIndex = pEnumIndex.Next If pIndex Is Nothing Then    ' Add Spatial Index End If This always fails suggesting the spatial index exists but I know it does not as another tool runs very slowly without it.Only when I restart ArcMap, load the shapefile, open attribute table do I see that the * in the shape field has disappeared.So my question is knowing that I use the IFeatureClass.AddField method to add a field how do I "refresh" ArcMap to pick up on the fact that the spatial index has been lost and allow my check for spatial index code to work? Duncan ... View more