Wrong current value on graph or table but correct in query inspector

Hello, My case is really specific but hope that someone could help me.

So in short, i have materialized view with summary information on amount of mailed users of my service. Example:

As i need optional aggregation (by day, week, month, year) - i’m generating timeseries this way:

(intDiv(toUInt32(toStartOfDay(send_time)), 1200) * 1200) * 1000                 AS period_day,
(intDiv(toUInt32(toStartOfDay(toStartOfWeek(send_time))), 1200) * 1200) * 1000  AS period_week,
(intDiv(toUInt32(toStartOfDay(toStartOfMonth(send_time))), 1200) * 1200) * 1000 AS period_month,
(intDiv(toUInt32(toStartOfDay(toStartOfYear(send_time))), 1200) * 1200) * 1000  AS period_year

Here is example of query:

SELECT
        multiIf('$period_of_aggregation' = 'week', period_week, '$period_of_aggregation' = 'month', period_month,
            '$period_of_aggregation' = 'year', period_year, period_day) as t,
      sum(sent) as sent
    FROM dc.mails_aggregated
    WHERE
        $timeFilter
        AND status = 'sent'
        AND dispatch_type in ($dispatch_type)
        AND domain in ($domains)
    GROUP BY t
    ORDER BY t

Issue: point of graph (or line in table) for current day differs value, returned by query inspector if picked timerange is more than 7days, if it’s 7days or less - value is correct.

Example: Table:

If i pick time range 7 days - value for current day becomes correct (105.24 K)

Same behavior is for graph representation.

I tried this on different grafana and CH-plugin versions, including latest. I’m ablre to reproduce this everywhere.

I will be grateful for your thoughts and advice.

[Slach]

value for last N datapoint in time series format extrapolated it’s described on FAQ https://github.com/Vertamedia/clickhouse-grafana#faq maybe this behavior should be optional

[kirik]

Thank you @Slach for explanation! And yes I think too that this behavior should be optional (or off by default) because it produce wrong numbers.