Is there any way to reduce the density of historical data？I mean, I saved per second, and it’s unnessessary for more then two years old data. But I don’t want loss all old data. Is there any way to reduce the rate to 1 minute for old data?
I’m thinking something like
delete from sqlt_data_X_YYYY_MM where extract(second from from_unixtime(t_stamp/1000)) / 10 != 0
There might be a better/cleaner syntax, but hey… This should delete all entries where the seconds are not between 00 and 09.
You can use the sqlth_partitions table to find all the historian data tables.
edit: Oh wait, you’re historizing every second… then
delete from sqlt_data_X_YYYY_MM where extract(second from from_unixtime(t_stamp/1000)) != 0
Would delete every entry where seconds are not 0.
Use at your own risks 
Haha，It’s worth trying. I’m just worried about whether the ignition will recognize the rest data.
What do you mean, the rest data ?
You’re afraid the remaining data will be corrupted ?
It won’t. Each row in those tables represent an individual data point, removing one shouldn’t break the others.
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ive deleted individual entries many times with no issue.
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