feat(bigquery): add interval support

bigquery/intervalvalue.go

@@ -0,0 +1,321 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package bigquery
+
+import (
+	"bytes"
+	"fmt"
+	"strconv"
+	"time"
+)
+
+// IntervalValue is a go type for representing BigQuery INTERVAL values.
+// Intervals are represented using three distinct parts:
+// * Years and Months
+// * Days
+// * Time (Hours/Mins/Seconds/Fractional Seconds).
+//
+// More information about BigQuery INTERVAL types can be found at:
+// https://cloud.google.com/bigquery/docs/reference/standard-sql/data-types#interval_type
+//
+// IntervalValue is EXPERIMENTAL and subject to change or removal without notice.
+type IntervalValue struct {
+	// In canonical form, Years and Months share a consistent sign and reduced
+	// to avoid large month values.
+	Years  int32
+	Months int32
+
+	// In canonical form, Days are independent of the other parts and can have it's
+	// own sign.  There is no attempt to reduce larger Day values into the Y-M part.
+	Days int32
+
+	// In canonical form, the time parts all share a consistent sign and are reduced.
+	Hours   int32
+	Minutes int32
+	Seconds int32
+	// This represents the fractional seconds as nanoseconds.
+	SubSecondNanos int32
+}
+
+// String returns string representation of the interval value using the canonical format.
+// The canonical format is as follows:
+//
+// [sign]Y-M [sign]D [sign]H:M:S[.F]
+func (iv *IntervalValue) String() string {
+	// Don't canonicalize the current value.  Instead, if it's not canonical,
+	// compute the canonical form and use that.
+	src := iv
+	if !iv.IsCanonical() {
+		src = iv.Canonicalize()
+	}
+	out := fmt.Sprintf("%d-%d %d %d:%d:%d", src.Years, int32abs(src.Months), src.Days, src.Hours, int32abs(src.Minutes), int32abs(src.Seconds))
+	if src.SubSecondNanos != 0 {
+		mantStr := fmt.Sprintf("%09d", src.SubSecondNanos)
+		for len(mantStr) > 0 && mantStr[len(mantStr)-1:] == "0" {
+			mantStr = mantStr[0 : len(mantStr)-1]
+		}
+		out = fmt.Sprintf("%s.%s", out, mantStr)
+	}
+	return out
+}
+
+// intervalPart is used for parsing string representations.
+type intervalPart int
+
+const (
+	yearsPart = iota
+	monthsPart
+	daysPart
+	hoursPart
+	minutesPart
+	secondsPart
+	subsecsPart
+)
+
+func (i intervalPart) String() string {
+	knownParts := []string{"YEARS", "MONTHS", "DAYS", "HOURS", "MINUTES", "SECONDS", "SUBSECONDS"}
+	if i < 0 || int(i) > len(knownParts) {
+		return fmt.Sprintf("UNKNOWN(%d)", i)
+	}
+	return knownParts[i]
+}
+
+// canonicalParts indicates the parse order for canonical format.
+var canonicalParts = []intervalPart{yearsPart, monthsPart, daysPart, hoursPart, minutesPart, secondsPart, subsecsPart}
+
+// ParseInterval parses an interval in canonical string format and returns the IntervalValue it represents.
+func ParseInterval(value string) (*IntervalValue, error) {
+	iVal := &IntervalValue{}
+	for _, part := range canonicalParts {
+		remaining, v, err := getPartValue(part, value)
+		if err != nil {
+			return nil, err
+		}
+		switch part {
+		case yearsPart:
+			iVal.Years = v
+		case monthsPart:
+			iVal.Months = v
+			if iVal.Years < 0 {
+				iVal.Months = -v
+			}
+		case daysPart:
+			iVal.Days = v
+		case hoursPart:
+			iVal.Hours = v
+		case minutesPart:
+			iVal.Minutes = v
+			if iVal.Hours < 0 {
+				iVal.Minutes = -v
+			}
+		case secondsPart:
+			iVal.Seconds = v
+			if iVal.Hours < 0 {
+				iVal.Seconds = -v
+			}
+		case subsecsPart:
+			iVal.SubSecondNanos = v
+			if iVal.Hours < 0 {
+				iVal.SubSecondNanos = -v
+			}
+		default:
+			return nil, fmt.Errorf("encountered invalid part %s during parse", part)
+		}
+		value = remaining
+	}
+	return iVal, nil
+}
+
+func getPartValue(part intervalPart, s string) (string, int32, error) {
+	s = trimPrefix(part, s)
+	return getNumVal(part, s)
+}
+
+// trimPrefix removes formatting prefix relevant to the given type.
+func trimPrefix(part intervalPart, s string) string {
+	var trimByte byte
+	switch part {
+	case yearsPart, daysPart, hoursPart:
+		trimByte = byte(' ')
+	case monthsPart:
+		trimByte = byte('-')
+	case minutesPart, secondsPart:
+		trimByte = byte(':')
+	case subsecsPart:
+		trimByte = byte('.')
+	}
+	for len(s) > 0 && s[0] == trimByte {
+		s = s[1:]
+	}
+	return s
+}
+
+func getNumVal(part intervalPart, s string) (string, int32, error) {
+
+	allowedVals := []byte("0123456789")
+	var allowedSign bool
+	captured := ""
+	switch part {
+	case yearsPart, daysPart, hoursPart:
+		allowedSign = true
+	}
+	// capture sign prefix +/-
+	if len(s) > 0 && allowedSign {
+		switch s[0] {
+		case '-':
+			captured = "-"
+			s = s[1:]
+		case '+':
+			s = s[1:]
+		}
+	}
+	for len(s) > 0 && bytes.IndexByte(allowedVals, s[0]) >= 0 {
+		captured = captured + string(s[0])
+		s = s[1:]
+	}
+
+	if len(captured) == 0 {
+		if part == subsecsPart {
+			return s, 0, nil
+		}
+		return "", 0, fmt.Errorf("no value parsed for part %s", part.String())
+	}
+	// special case: subsecs is a mantissa, convert it to nanos
+	if part == subsecsPart {
+		parsed, err := strconv.ParseFloat(fmt.Sprintf("0.%s", captured), 64)
+		if err != nil {
+			return "", 0, fmt.Errorf("couldn't parse %s as %s", captured, part.String())
+		}
+		return s, int32(parsed * 1e9), nil
+	}
+	parsed, err := strconv.ParseInt(captured, 10, 32)
+	if err != nil {
+		return "", 0, fmt.Errorf("error parsing value %s for %s: %v", captured, part.String(), err)
+	}
+	return s, int32(parsed), nil
+}
+
+// IntervalValueFromDuration converts a time.Duration to an IntervalType representation.
+//
+// The converted duration only leverages the hours/minutes/seconds part of the interval,
+// the other parts representing days, months, and years are not used.
+func IntervalValueFromDuration(in time.Duration) *IntervalValue {
+	nanos := in.Nanoseconds()
+	out := &IntervalValue{}
+	out.Hours = int32(nanos / 3600 / 1e9)
+	nanos = nanos - (int64(out.Hours) * 3600 * 1e9)
+	out.Minutes = int32(nanos / 60 / 1e9)
+	nanos = nanos - (int64(out.Minutes) * 60 * 1e9)
+	out.Seconds = int32(nanos / 1e9)
+	nanos = nanos - (int64(out.Seconds) * 1e9)
+	out.SubSecondNanos = int32(nanos)
+	return out
+}
+
+// ToDuration converts an interval to a time.Duration value.
+//
+// For the purposes of conversion:
+// Years are normalized to 12 months.
+// Months are normalized to 30 days.
+// Days are normalized to 24 hours.
+func (iv *IntervalValue) ToDuration() time.Duration {
+	var accum int64
+	accum = 12*int64(iv.Years) + int64(iv.Months)
+	// widen to days
+	accum = accum*30 + int64(iv.Days)
+	// hours
+	accum = accum*24 + int64(iv.Hours)
+	// minutes
+	accum = accum*60 + int64(iv.Minutes)
+	// seconds
+	accum = accum*60 + int64(iv.Seconds)
+	// subsecs
+	accum = accum*1e9 + int64(iv.SubSecondNanos*1e9)
+	return time.Duration(accum)
+}
+
+// Canonicalize returns an IntervalValue where signs for elements in the
+// Y-M and H:M:S.F are consistent and values are normalized/reduced.
+//
+// Canonical form enables more consistent comparison of the encoded
+// interval.  For example, encoding an interval with 12 months is equivalent
+// to an interval of 1 year.
+func (iv *IntervalValue) Canonicalize() *IntervalValue {
+	newIV := &IntervalValue{iv.Years, iv.Months, iv.Days, iv.Hours, iv.Minutes, iv.Seconds, iv.SubSecondNanos}
+	// canonicalize Y-M part
+	totalMonths := iv.Years*12 + iv.Months
+	newIV.Years = totalMonths / 12
+	totalMonths = totalMonths - (newIV.Years * 12)
+	newIV.Months = totalMonths % 12
+
+	// No canonicalization for the Days part.
+
+	// canonicalize time part by switching to Nanos.
+	totalNanos := int64(iv.Hours)*3600*1e9 +
+		int64(iv.Minutes)*60*1e9 +
+		int64(iv.Seconds)*1e9 +
+		int64(iv.SubSecondNanos)
+
+	// Reduce to parts.
+	newIV.Hours = int32(totalNanos / 60 / 60 / 1e9)
+	totalNanos = totalNanos - (int64(newIV.Hours) * 3600 * 1e9)
+	newIV.Minutes = int32(totalNanos / 60 / 1e9)
+	totalNanos = totalNanos - (int64(newIV.Minutes) * 60 * 1e9)
+	newIV.Seconds = int32(totalNanos / 1e9)
+	totalNanos = totalNanos - (int64(newIV.Seconds) * 1e9)
+	newIV.SubSecondNanos = int32(totalNanos)
+	return newIV
+}
+
+// IsCanonical evaluates whether the current representation is in canonical
+// form.
+func (iv *IntervalValue) IsCanonical() bool {
+	if !sameSign(iv.Years, iv.Months) ||
+		!sameSign(iv.Hours, iv.Minutes) {
+		return false
+	}
+	// We allow large days and hours values, because they are within different parts.
+	if int32abs(iv.Months) > 12 ||
+		int32abs(iv.Minutes) > 60 ||
+		int32abs(iv.Seconds) > 60 ||
+		int32abs(iv.SubSecondNanos) > 1e9 {
+		return false
+	}
+	// TODO: We don't currently validate that each part represents value smaller than 10k years.
+	return true
+}
+
+func int32abs(x int32) int32 {
+	if x < 0 {
+		return -x
+	}
+	return x
+}
+
+func sameSign(nums ...int32) bool {
+	var pos, neg int
+	for _, n := range nums {
+		if n > 0 {
+			pos = pos + 1
+		}
+		if n < 0 {
+			neg = neg + 1
+		}
+	}
+	if pos > 0 && neg > 0 {
+		return false
+	}
+	return true
+}