Can anyone give me some direction on using Ignition to access trend data from a compressed Rockwell Historian database?
I have a customer that uses Rockwell Historian with compression. I have some information on how to use some special SQL commands in coordination with database views to get data out of the tables, but it seems a bit convoluted. Does Ignition have any built in capabilities to allow direct SQL queries to the Historian data?
If you can establish a connection to this historian data, you’d be able to issue those queries, but making the connection comes first. JDBC is probably wishful thinking, but maybe an ODBC connection would work? I’m guessing here because I’m not familiar with that product at all…
The connection is not the issue. The issue is that Rockwell Historian does a proprietary compression of the data going into the tables. Any query to the tables requires decompression of the data. Rockwell has documentation on how to query and decompress this data, but I was curious if Ignition had any built in features for doing this. It appears that it doesn’t.
being that the Rockwell compression is proprietary, I wouldn’t expect any other product to be supporting access to it…
I have never tried it but there is a view named UnCompress, you might try with:
SELECT * FROM UnCompress
It seems that you have to set up some security settings in MSSQL in order to use that view, but I guess it can be done with not too much effort.
That view uses a function named fnUncompress() where there is all the decompressing logic
Hope this helps.