Measurement List for each device in openHistorian

GPA Products openHistorian
1

Hi,
Is there a query by which we can get the list of measurements for each of the devices in openHistorian?
Thanks and regards,
Dattatreya

2

You can do this with a SQL query:

For all measurement records by device:

SELECT * FROM ActiveMeasurement ORDER BY Device

For a particular device:

SELECT * FROM ActiveMeasurement WHERE Device = 'SHELBY'

Is this what you are asking?

If you are using the openHistorian Python code, the metadata can already be filtered by device.

Thanks,
Ritchie

3

Hi Ritchie,
This is exactly what I tried but I am not getting any output. Can you provide me with the Python equivalent of this?
Thanks,
Datta

4 
# Connect to historian
# code omitted for brevity, see: https://pypi.org/project/openhistorian/

# Get a reference to the openHistorian metadata cache
historian.RefreshMetadata()
metadata = historian.Metadata

device = metadata.LookupDeviceByAcronym("SHELBY")
deviceMeasurements = device.Measurements
5

Thanks Ritchie for the reference

6

Hi Ritchie,
I am getting an error while executing the code. For executing this code which methods do we need to import?

7

I expect something like this:

from openHistorian.historianConnection import historianConnection
from openHistorian.historianInstance import historianInstance
from openHistorian.metadataCache import metadataCache
from openHistorian.deviceRecord import deviceRecord
from openHistorian.measurementRecord import measurementRecord
8

Hi Ritchie,
This is my code and this is the error that I am getting:

from openHistorian.historianConnection import historianConnection

from openHistorian.historianInstance import historianInstance

from openHistorian.historianKey import historianKey

from openHistorian.historianValue import historianValue

from openHistorian.metadataCache import metadataCache

from openHistorian.measurementRecord import SignalType, measurementRecord

from openHistorian.deviceRecord import deviceRecord

from snapDB.timestampSeekFilter import timestampSeekFilter

from snapDB.pointIDMatchFilter import pointIDMatchFilter

from snapDB.enumerations import QualityFlags

from gsf import Ticks

from typing import Optional, List

from datetime import datetime, timedelta

from time import time

import numpy as np

import math

import pandas as pd

import itertools

import smtplib

from email.message import EmailMessage

def readTest():

    # Create historian connection (the root API object)

    historian = historianConnection("localhost")

    instance: Optional[historianInstance] = None

    
    

    try:

        print("Connecting to openHistorian...")

        historian.Connect()

        if not historian.IsConnected or len(historian.InstanceNames) == 0:

            print("No openHistorian instances detected!")

        else:

            # Get first historian instance

            initialInstance = historian.InstanceNames[0]

            print(f"Opening \"{initialInstance}\" database instance...")

            instance = historian.OpenInstance(initialInstance)

            key = historianKey()

            value = historianValue()

            # Get a reference to the openHistorian metadata cache

            historian.RefreshMetadata()

            metadata = historian.Metadata

            device = metadata.LookupDeviceByAcronym("ECROWE")

            deviceMeasurements = device.Measurements

            print(deviceMeasurements)

    except Exception as ex:

        print(f"Failed to connect: {ex}")

    finally:

        if instance is not None:

            instance.Dispose()

        if historian.IsConnected:

            print("Disconnecting from openHistorian")

        historian.Disconnect()

if __name__ == "__main__":

    readTest()

Error:
Failed to connect: ‘NoneType’ object has no attribute ‘Measurement’

9

If you remove the try/catch (or debug) can you determine on which line it is failing?

10

Hi Ritchie,
The error is in the following line:

deviceMeasurements = device.Measurements
AttributeError: ‘NoneType’ object has no attribute 'Measurements’

11

Ah, device was not found:

acronym = "SHELBY"
device = metadata.LookupDeviceByAcronym(acronym)

if device is not None:
    deviceMeasurements = device.Measurements
else
    raise RuntimeError(f"Failed to find device '{acronym}'")
12

Not exactly. The device is there on openHistorian. Attaching the screenshot of the same

image
image1916×418 120 KB

13

Click on Edit beside ECROWE device and verify Acronym

Also, you should be able to enumerate device acronyms in Python metadata using print to verify you are using correct acronym name.

The screen you are looking at sometimes will remove a subscription prefix like GEP! for brevity.

Thanks,
Ritchie