You can enable Subset Mode in MongoDB Charts to restrict
the input collection to
1000 randomly selected documents. To toggle
Subset Mode, use the toggle in the Preview
section. The Subset Mode setting for a chart doesn't
persist when the chart renders on a dashboard. So, if you enable
subset mode when you build a chart, the data that renders in the
dashboard isn't sampled.
When you enable subset mode and you specify a filter, MongoDB Charts takes the sample of
documents before it applies the filter. So, MongoDB Charts might use
1000 documents to plot the chart.
Consider using Subset Mode when you draft a chart and heavily modify chart options. In this situation, Subset Mode lets the chart render quickly during the building process. When you feel satisfied with your chart, save it as soon as possible.
Due to the random nature of sampling, when you have Subset Mode enabled, your visualizations might change each time the chart loads in the chart builder.