Most numeric datatypes index extra terms representing numeric ranges for each number to make range queries faster. For instance, this range query:

  "range": {
    "number": {
      "gte": 0
      "lte": 321
    }
  }

might be executed internally as a terms query that looks something like this:

  "terms": {
    "number": [
      "0-255",
      "256-319"
      "320",
      "321"
    ]
  }

These extra terms greatly reduce the number of terms that have to be examined, at the cost of increased disk space.

The default value for precision_step depends on the type of the numeric field:

The value of the precision_step setting indicates the number of bits that should be compressed into an extra term. A long value consists of 64 bits, so a precision_step of 16 results in the following terms: