Units of interval in database

[Peter Cooper-Davis]

I recently noticed some issues with my weewx database when calculating average values from the weighted daily sums compared to from the individual records. For example:

select avg(outTemp) from archive where strftime("%m", dateTime,'unixepoch','localtime')=='09'; gives 16.44376...

select sum(sum)/sum(count) from archive_day_outTemp where strftime("%m", dateTime,'unixepoch','localtime')=='09'; gives 16.44402...

BUT

select sum(wsum)/sum(sumtime) from archive_day_outTemp where where strftime("%m", dateTime,'unixepoch','localtime')=='09'; gives 12.76334...

I looked into my database in more detail and noticed that some days have a much higher count and sumtime than others despite the same record count. Following this discrepancy further, I then noticed that on the days with the larger sumtime, some of my records had an interval of 300 and some had a interval of 5.

This brings me to my question. What is the unit of interval in the database? I had assumed it was seconds (which matches the units of archive_interval in weewx.conf), so the records with an interval of 300 are 5-minute averaged catch-up records generated through my drivers genStartupRecords() where I manually specify the interval to be 300 seconds. The records with an internal of 5 are generated from loop packets. I suspect my issue is that the units of interval is minutes, and therefore I should change 300 to 5 in my genStartupRecords() function and manually adjust my database to change all instances of interval=300 to interval=5 (I have always used a constant archive interval). Before I do this though, can someone confirm that my thinking is correct?

[Tom Keffer]

Your suspicion is correct. The unit for `interval` is minutes. I know it's not consistent with the rest of WeeWX, but we inherited it from the wview schema. 

See the section The database in the Customization Guide.

-tk

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[Peter Cooper-Davis]

Not sure how I missed that in the Customisation Guide! Thanks for clarifying though. I’ll update the interval in the archive table and then drop/rebuild the daily summaries