Amazon CloudSearch
Developer Guide (API Version 2013-01-01)

Getting Statistics for Numeric Fields in Amazon CloudSearch

Amazon CloudSearch can return the following statistics for facet-enabled numeric fields:

  • count–The number of documents that contain a value in the specified field.

  • max–The maximum value found in the specified field.

  • mean–The average of the values found in the specified field.

  • min–The minimum value found in the specified field.

  • missing–The number of documents that do not contain a value in the specified field.

  • stddev–A measure to quantify the amount of deviation, or variation, in the field values. A low standard deviation indicates that the values across all documents are close to the mean. A high standard deviation indicates that the values are spread out over a large range. The standard deviation is calculated by taking the square root of the variance, which is the average of the squared differences from the mean.

  • sum–The sum of the field values across all documents.

  • sumOfSquares–The sum of all field values squared.

To get statistics for a field you use the stats.FIELD parameter. FIELD is the name of a facet-enabled numeric field. You specify an empty JSON object, stats.FIELD={}, to get all of the available statistics for the specified field. (The stats.FIELD parameter does not support any options; you must pass an empty JSON object.) You can request statistics for multiple fields in the same request.

You can get statistics only for facet-enabled numeric fields: date, date-array, double, double-array, int, or int-array. Note that only the count, max, min, and missing statistics are returned for date and date-array fields. For more information about enabling a field to return facets, see configure indexing options.

For example, to search for star and get statistics for the year field, specify the following: