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Chart Cache Minutes: - by default, this is 0 (zero) meaning the chart data is not cached. If this was set to 60 then the first time a given SQL query from piDashboard was executed the result would be cached for the next 59 minutes and 59 seconds. Within that time period anyone looking at the same chart would get the same result as the original user got; the SQL would not be executed again. After 60 minutes have passed then the SQL wouldbe re-executed, and then the clock would reset for another 59 minutes and 59 seconds. If you are connecting to a Data Warehouse for example, then it makes sense to set this to a higher number as the data is not going to be constantly changing and there is little point re-executing the SQL whilst the data is static.
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This setting might be worth considering if your data is only updated once a day. |
Max Rows: - this only applies to data tables. If this was set to 5,000 then any data tables built using this data connection would be limited to display only the first 5,000 rows retrieved. As the data in data tables can take some time to render (also depending on the number of columns) this helps address potential performance issues. This parameter does not apply to charts, if this was set to 5,000 but a given chart needed to read from 10m rows of data then it would be able to do so. This setting also applies to exporting - if a data table is exported, the number of rows included in the export will be determined by the number set here.
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