Historizing a large JSON string tag

roger_larson
Mon, 26 Feb 2018 21:57:38 +0000
Ignition

Hi all,

I have a problem storing data from a tag containing a JSON string (or Python dictionary, if you will) within Ignition. Generally, the string exceeds the VARCHAR(255) character limit that is implemented in the tag historian tables (stringvalue column). Thus, a MySQL table cannot accept the value and refuses to historize it, causing the values to aggregate in store and forward.

I also cannot automate an alteration of that table column to VARCHAR(8191) or whatever, since tables are partitioned by day and millions of rows are being stored - tables that already exist are difficult to modify without errors, this may be unreliable.

Anyone have a good, alternative solution to this? Breaking the JSON string up into multiple columns? Turning the data into tags?

Best Regards,
Roger

4 posts - 4 participants