Function sqlStdToDuration

pkg/util/duration/parse.go:182–402

Parses a SQL standard interval string. See the following links for examples: - http://www.postgresql.org/docs/9.1/static/datatype-datetime.html#DATATYPE-INTERVAL-INPUT-EXAMPLES - http://www.ibm.com/support/knowledgecenter/SSGU8G_12.1.0/com.ibm.esqlc.doc/ids_esqlc_0190.htm

(s string, itm types.IntervalTypeMetadata)

//   - http://www.postgresql.org/docs/9.1/static/datatype-datetime.html#DATATYPE-INTERVAL-INPUT-EXAMPLES
//   - http://www.ibm.com/support/knowledgecenter/SSGU8G_12.1.0/com.ibm.esqlc.doc/ids_esqlc_0190.htm
func sqlStdToDuration(s string, itm types.IntervalTypeMetadata) (Duration, error) {
	var d Duration
	parts := strings.Fields(s)
	if len(parts) > 3 || len(parts) == 0 {
		return d, newInvalidSQLDurationError(s)
	}
	// Index of which part(s) have been parsed for detecting bad order such as `HH:MM:SS Year-Month`.
	parsedIdx := nothingParsed
	// Both 'Day' and 'Second' can be float, but 'Day Second'::interval is invalid.
	floatParsed := false
	// Parsing backward makes it easy to distinguish 'Day' and 'Second' when encountering a single value.
	//   `1-2 5 9:` and `1-2 5`
	//        |              |
	// day ---+              |
	// second ---------------+
	for i := len(parts) - 1; i >= 0; i-- {
		// Parses leading sign
		part := parts[i]

		consumeNeg := func(str string) (newStr string, mult int64, ok bool) {
			neg := false
			// Consumes [-+]
			if str != "" {
				c := str[0]
				if c == '-' || c == '+' {
					neg = c == '-'
					str = str[1:]
				}
			}
			if len(str) == 0 {
				return str, 0, false
			}
			if str[0] == '-' || str[0] == '+' {
				return str, 0, false
			}

			mult = 1
			if neg {
				mult = -1
			}
			return str, mult, true
		}

		var mult int64
		var ok bool
		if part, mult, ok = consumeNeg(part); !ok {
			return d, newInvalidSQLDurationError(s)
		}

		if strings.ContainsRune(part, ':') {
			// Try to parse as HH:MM:SS
			if parsedIdx != nothingParsed {
				return d, newInvalidSQLDurationError(s)
			}
			parsedIdx = hmsParsed
			// Colon-separated intervals in Postgres are odd. They have day, hour,
			// minute, or second parts depending on number of fields and if the field
			// is an int or float.