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Could this be better (data transfer Access -> SDE)?

evtguy

Of all the programming languages I know and use, Python is at the bottom so I want to post this script to see if what I have is as efficient as it can be. The Backstory: Our organization has a web map showing stream gage information. The gage information comes into and is stored in an Access. The third party stream gage software runs an annual maintenance on the Access database so we cannot just link to the table directly because that would conflict with database maintenance that occurs.

My solution was to develop a simple script which would connect to the Access database, select all records in a given query, and then transfer that information over to a table in SDE which, in turn, is consumed by the map's services. The script runs as a windows task every five minutes and performs an initial test to see if it's "safe" to connect to the Access Database. If it is, the data is read and passed on to the table. The number of rows in the Access database on average is roughly 2200-2400 records. Initially, the script took about 40 seconds to run but lately it has taken longer. (hence my post about it).

So- here is the script. I've left all the comments in it so hopefully there's not any confusion about what's happening. Is there a better way to approach and accomplish this task? Thanks!

Steve

Script:

import sys
import os
import linecache
import logging
import arcpy
from datetime import datetime
from arcpy import env


file01 = r"\\pmc-floodwatch\DIADvisorDatabases\DvLive.mok" #This file must exist
file02 = r"\\pmc-floodwatch\DIADvisorDatabases\DvLive.mno" #This file must NOT exist
expression = '1=1' #SQL shorthand which select all records
theTable = "tblGageData"


#Establish the error log file 
logger = logging.getLogger('errorLog')
hdlr = logging.FileHandler(r'\\snoco\gis\pw\tes\spwscc\python\errorLog.log')
logger.addHandler(hdlr)


# The tables within DIADvisor must not be accessed during its daily database maintenance.
# OneRain recommends checking for the existence and non-existence of two specific files.
# If both conditions are true, it is safe to proceed with connecting to the data within
# the dvLive Access database
if os.path.exists(file01) and not os.path.exists(file02):
        print "Processing start time: " + str(datetime.now())
        
        env.workspace = r"C:\gishome\tasks\flood_warning_system\_SPW_GDBMGR@GIS_PW_SWM.sde"
        try:
                # Set some local variables
                tempTableView = "gageTableView"


                # Execute MakeTableView
                arcpy.MakeTableView_management(theTable, tempTableView)


                # Execute SelectLayerByAttribute to select all records
                arcpy.SelectLayerByAttribute_management(tempTableView, "NEW_SELECTION", expression)


                # Execute GetCount and if some records have been selected, then execute
                #  DeleteRows to delete the selected records.
                if int(arcpy.GetCount_management(tempTableView).getOutput(0)) > 0:
                        arcpy.DeleteRows_management(tempTableView)
                
                # Now connect to the DIADvisor access database and import the most recent data
                # This requires the OLD DB connection previously established using ArcCatalog
                counter = 0


                accessRows = arcpy.SearchCursor(r"C:\gishome\tasks\flood_warning_system\jetConnectForDvLive.odc\last3days")
                curSde = arcpy.InsertCursor(r"C:\gishome\tasks\flood_warning_system\_SPW_GDBMGR@GIS_PW_SWM.sde\tblGageData")
                # Loop through the results returned via the OLE DB connection
                for cRow in accessRows:
                    curSensorId = cRow.sensor_id
                    curEpoch = cRow.epoch
                    curData = cRow.data
                    curDataValue2 = cRow.dataValue2                                     
                    counter += 1


                    #Insert a new row into the SDE table with the current DIADvisor record's information
                    row = curSde.newRow()
                    row.SENSOR_ID = curSensorId
                    row.EPOCH = curEpoch
                    row.DATA = curData
                    row.dataValue2 = curDataValue2
                    curSde.insertRow(row)
                
                # We're done so perform some variable cleanup
                del row
                del accessRows
                del curSde
                del cRow
                print "Number of record(s) in the DIADvisor database: " + str(counter)
                print "Processing end time: " + str(datetime.now())
        except Exception as e:
                # If an error occurred, print line number and error message
                exc_type, exc_obj, exc_tb = sys.exc_info()
                fname = os.path.split(exc_tb.tb_frame.f_code.co_filename)[1]
                theMessage = "\n" + 80*"#" + "\n" + 80*"#" + "\n"
                theMessage = theMessage + "DATE/TIME: " + str(datetime.now()) + ":" + "\n"
                theMessage = theMessage + "EXECPTION: " + str(e) + "\n" + "\n"
                theMessage = theMessage + "CALLBACK TRACE: " + "\n"
                theMessage = theMessage + 20*" " + "File: " + str(exc_tb.tb_frame.f_code.co_filename) + "\n"
                theMessage = theMessage + 20*" " + "Line " + str(exc_tb.tb_lineno) + ": " + str(linecache.getline(exc_tb.tb_frame.f_code.co_filename, exc_tb.tb_lineno))
                theMessage = theMessage + 20*" " + "Exception Type: " + str(exc_type)
                print theMessage
                logger.error(theMessage)
else:
        sys.exit()

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Accepted answers

All comments

blake.terhune

There are some basic examples in the Esri help documentation

ArcGIS Help 10.2 - SearchCursor (arcpy.da)

For your particular code, it's as simple as just starting with the cursors in nested with statements and removing the del lines afterwards.

with arcpy.SearchCursor(r"C:\gishome\tasks\flood_warning_system\jetConnectForDvLive.odc\last3days") as accessRows:
    with arcpy.InsertCursor(r"C:\gishome\tasks\flood_warning_system\_SPW_GDBMGR@GIS_PW_SWM.sde\tblGageData") as curSde:
        for cRow in accessRows:
            # Loop through the results returned via the OLE DB connection
            ##

            #Insert a new row into the SDE table with the current DIADvisor record's information
            ##

print "Number of record(s) in the DIADvisor database: " + str(counter)
print "Processing end time: " + str(datetime.now())

evtguy

Blake T‌ I have switched my code base over to using the da module and it runs successfully. Can you point me to a code sample that illustrates using the "with" statement?

blake.terhune

I second this. Use the arcpy.da module for cursors and use them in a with statement so the cursors are automatically deleted even if there was an error. Your current code may not delete the cursors if there was an error.

JamesCrandall

Well... this sure sounds like a database management task. Handling it at the database seems far more reasonable, scalable and maintainable compared to messy scripting that will be subjected to failure over time as system-level changes occur.

I'd get with the DBA and work it out.

evtguy

James Crandall‌

Honestly, I don't know. This just seemed like a reasonable approach to me at the time.

I'm not completely sure about what you're suggesting. Are you talking about simply importing the table into SDE everytime the task scheduler runs? I kinda thought about that but since the table is also being consumed in a map service, I wondered if deleting it would cause issues (albeit it would only be deleted for a fraction of time).

evtguy

So, the connection string to SDE is using operating system authentication instead of database authentication. Would I need to use db authentication instead? And then, which account? SDE?

JamesCrandall

Why not just setup a scheduled import package on the RDBMS to just update the table? Seems like the best way to manage tabular data is at the database rather than some external app that needs to be executed and maintained.

Christian_Wells

Hi Steve, we would just need to use the account of the data owner. In ArcCatalog, you may see the feature class displayed as "SDE.tblGageData". In this case, "SDE" would be the data owner. To overcome this, the username from the database connection would need to match.

evtguy

Christian Wells‌

So, I was making the change from deleteRows to truncate and got the following message:

"ERROR 001400: Only the data owner may execute truncate."

I'm not quite sure what to do about this. I was running the script manually but using the same db connection string that our automated task uses. How do I overcome this?

evtguy

Thanks. guys. This is exactly the kind of feedback I was hoping for.

Christian Wells‌ yes- the SDE table is wiped clean before the records are transferred. The table is not registered as versioned so that won't be a problem.

Christian_Wells

In your script it appears you are deleting ALL records from the SDE table prior to the insert. Is the goal to remove all the records prior to the insert cursor?

If this is such the case, I would not recommend using the Delete Rows command, but rather the Truncate Table command. In SQL, truncate is much more efficient than delete. However, this requires that your table is not registered as versioned.

jskinner

Hi Steve,

One way to speed up your script is to use the data access module (arcpy.da). ArcGIS 10.1 introduced this and the performance is much faster than the previous search/insert/update cursors.

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