Function formatURLForCache

database/sqlite/sharded.go:650–687

Format URL for a specific shard Basically, remove start/end if is is before/after shard time

(uRL *url.URL, shardName int, startMonth int, endMonth int, timeRange *database.TimeRange)

// Format URL for a specific shard
// Basically, remove start/end if is is before/after shard time
func formatURLForCache(uRL *url.URL, shardName int, startMonth int, endMonth int, timeRange *database.TimeRange) (string, error) {
	// Extract URL query parameters
	queryParams := uRL.Query()

	// Remove start
	if startMonth < shardName {
		queryParams.Del("start")
	}

	// Remove start if timeRange.Start is the start of current month
	if startMonth == shardName && isStartOfMonth(timeRange.Start) {
		queryParams.Del("start")
	}

	// Remove end
	if endMonth > shardName {
		queryParams.Del("end")
	}

	// Remove cache for months before current month
	currentMonth, err := shardNameToInt(timeToShardName(time.Now().UTC()))
	if err != nil {
		return "", err
	}

	if shardName < currentMonth {
		queryParams.Del("cache")
	}

	// Add shard=shardName query parameter
	queryParams.Add("shard", strconv.Itoa(shardName))

	// Create new modified URL
	cacheURL := *uRL
	cacheURL.RawQuery = queryParams.Encode()

	return cacheURL.String(), nil
}

func isStartOfMonth(t time.Time) bool {
	y := t.Year()