Query a registered time series cache for data within a timestamp range, immediately returning any cached data. Missing data is retrieved from the data source in the background. Call repeatedly to obtain additional data as it arrives.
system.db.getSeriesCache(handle, [priority,] begints, endts, [gapTolerance,] valuecolumns) returns Dataset
|Numeric handle from registerSeriesCache().
|Optional, non-negative. One if omitted. Systemwide bulk queries for missing data will be executed in priority order. EasyNoteChart uses priority=1 for chart data and priority=2 for histogram data.
|Query start timestamp. Must not be null.
|Query end timestamp. Must not be null.
|Optional, Milliseconds. Insert a null row when consecutive timestamps are further apart than this tolerance.
|List of Strings defining the value columns to be delivered.
If there is a chance you won't call the getSeriesCache() function often enough to keep the handle from expiring, you should wrap a first attempt in a try/except block, where the except clause obtains a fresh handle.
The Dataset returned is actually a supporting subclass: TransientSeriesFragment. It carries additional properties and methods that can describe the progress of the cache query. It also excludes its rows from most serialization, avoiding storing large datasets in your projects.
See the timeSeriesCache expression function for a description of the underlying cache behavior.