[Question] Potential issues manually querying tag history?

Ignition
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1

Hello all,

I was wondering if someone could give more detail as to why manually querying tag history is not recommended. Looking at this article, it says that Ignition offers a variety of ways to query the data but does not recommend manually querying.

Although, I have a client who requests that the production database house only the last 90 days of data. Their policies state they cannot delete any data, so I built a SQL script that creates a backup database when the size reaches 8GB, as well as a table and inserts the tag history that is older than 90 days into these. After inserting, the records will be deleted from the production database

Normally I would not need to do this, but they have the EXPRESS version of SQL which is limited to 10GB per database. So far through testing I haven't seen any issues with this. Just want to make sure there won't be any unforeseen errors in the future.

Thank you!

2

No guarantee at all. The historian's table structures and behaviors are an implementation detail. The only long-term supported way to access history is with the system.tag.* functions.

That said, it isn't likely to change significantly any time soon. Meanwhile, you should advise your customer to abandon SQL Server Express. If $$ are the problem, they should be using PostgreSQL or MariaDB. Those have no limits, and in my not-so-humble opinion, are technically superior, too.

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Interesting, I will look into PostgreSQL and MariaDB and see which would fit best for the client. They have used Express in the past as they are a fairly small company. In about 10-15 years they only filled their DB to about 5GB.

Between the two you mentioned, is there one you would recommend over the other?

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I default to PostgreSQL. (It's more standards-compliant, and I think it has greater extendability.)

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Thank you sir!