The Cumulative Sum Aggregation is a parent pipeline aggregation that calculates the cumulative sum of a specified metric in a parent histogram (or date_histogram) aggregation. It computes a running total over the buckets of the parent histogram.
Syntax
{
"cumulative_sum": {
"buckets_path": "string"
}
}
For detailed syntax and parameters, refer to the official Elasticsearch documentation.
Example Usage
Here's an example of using the Cumulative Sum Aggregation to calculate the running total of sales over time:
{
"aggs": {
"sales_per_month": {
"date_histogram": {
"field": "date",
"calendar_interval": "month"
},
"aggs": {
"sales": {
"sum": {
"field": "price"
}
},
"cumulative_sales": {
"cumulative_sum": {
"buckets_path": "sales"
}
}
}
}
}
}
Common Issues
- Incorrect parent aggregation: The Cumulative Sum Aggregation must be used with a histogram or date_histogram parent aggregation.
- Invalid buckets_path: Ensure the buckets_path correctly points to a metric aggregation within the parent histogram.
- Missing data: Gaps in the data can lead to unexpected results in the cumulative sum.
Best Practices
- Use date_histogram with appropriate time intervals for time-based cumulative sums.
- Consider using the "format" parameter to control the output format of the cumulative sum values.
- Combine with other aggregations like "derivative" to analyze rate of change in the cumulative sum.
Frequently Asked Questions
Q: Can I use Cumulative Sum Aggregation with non-numeric fields?
A: No, the Cumulative Sum Aggregation works only with numeric metrics. Ensure your target field is of a numeric type.
Q: How does Cumulative Sum Aggregation handle missing values?
A: By default, missing values are treated as zeros. You can use the "gap_policy" parameter to change this behavior.
Q: Can I reset the cumulative sum at specific intervals?
A: The Cumulative Sum Aggregation doesn't have a built-in reset feature. For resets, you might need to use scripted metrics or post-process the results.
Q: Is it possible to calculate a cumulative sum in reverse order?
A: The Cumulative Sum Aggregation calculates in forward order by default. For reverse order, you'd need to reverse the buckets in your application logic after receiving the results.
Q: How does Cumulative Sum Aggregation impact query performance?
A: As a pipeline aggregation, it doesn't significantly impact query performance since it operates on already aggregated data. However, the parent histogram aggregation's size can affect overall query time.
