I have tested with Ignition 7.9.7 AND 8.03 so I will report it for version 8
imode = system.tag.read(atag+".InterpolationMode").getValue() returns different answers depending on the tagpath (for the same tag).
Full or partial path should give same result, but the partial path is the one that gives the correct result.
full tag path:
both return same trend data, but the full path returns InterpolationMode as None
and the partial path returns InterpolationMode as Discrete when using system.tag.read as noted above.
I am writing this from home so I don’t have the database version, but it is Mariadb, fairly recent version.
OS is Ubuntu 18,04 for the test with Ignition 8
OS is Ubuntu 16.04 for the test with Ignition 7.9.7 and the database here is MSSQL 2014
One additional note is that Ignition 7.9.7 returns 0 or 3
while Ignition 8.0.3 returns Discrete or None.
To setup for the test, Install Ignition 8.0.3, and a database, and create a database named process.
set the default history provider to be the process database
create a history tag, save it. then go back and change it to have (old terminology = InterpolationMode (Value Mode)) of Discrete. I think the terminology in 8.0.3 is something different like Deadband Style, but the InterpolationMode property gives the same result.
Why does it matter: I use the InterpolationMode to process the data differently depending on the value. I normally get the tagpath from the tag browser which returns the full path, which does not work correctly for this purpose.