Quantity  *Operand     `parser:" @@ \",\""`
	Timestamp *PrimaryTerm `parser:" @@ \")\""`
}

// DateDiffFunc represents the DATE_DIFF function
type DateDiffFunc struct {
	DatePart   string       `parser:" \"DATE_DIFF\" \"(\" @( \"YEAR\":Timeword | \"MONTH\":Timeword | \"DAY\":Timeword | \"HOUR\":Timeword | \"MINUTE\":Timeword | \"SECOND\":Timeword ) \",\" "`
	Timestamp1 *PrimaryTerm `parser:" @@ \",\" "`

			query:      `SELECT date_diff(year, '2010-01-01T', '2011-01-01T') FROM S3Object LIMIT 1`,
			wantResult: `{"_1":1}`,
		},
		{
			name:       "date_diff_year",
			query:      `SELECT date_diff(month, '2010-01-01T', '2010-05T') FROM S3Object LIMIT 1`,
			wantResult: `{"_1":4}`,
		},
		{
			name:       "date_diff_month_oney",
			query:      `SELECT date_diff(month, '2010T', '2011T') FROM S3Object LIMIT 1`,

- Large numbers (outside of the signed 64-bit range) are not yet supported.
- The Date [functions](https://docs.aws.amazon.com/AmazonS3/latest/dev/s3-glacier-select-sql-reference-date.html) `DATE_ADD`, `DATE_DIFF`, `EXTRACT` and `UTCNOW` along with type conversion using `CAST` to the `TIMESTAMP` data type are currently supported.

}

// dateDiff computes the difference between two times in terms of the
// `timePart` which can be years, months, days, hours, minutes or
// seconds. For difference in years, months or days, the time part,
// including timezone is ignored.
func dateDiff(timePart string, ts1, ts2 time.Time) (*Value, error) {
	if ts2.Before(ts1) {
		v, err := dateDiff(timePart, ts2, ts1)
		if err == nil {

	case sqlFnDateAdd:
		result.combine(e.DateAdd.Quantity.analyze(s))
		result.combine(e.DateAdd.Timestamp.analyze(s))
		return result

	case sqlFnDateDiff:
		result.combine(e.DateDiff.Timestamp1.analyze(s))
		result.combine(e.DateDiff.Timestamp2.analyze(s))
		return result

	// Handle aggregation function calls
	case aggFnAvg, aggFnMax, aggFnMin, aggFnSum, aggFnCount:
		// Initialize accumulator