func()

in tsdb/index/index.go [1491:1589]

• 82 lines of code
• 24 McCabe index (conditional complexity)

func (r *Reader) Postings(name string, values ...string) (Postings, error) {
	if r.version == FormatV1 {
		e, ok := r.postingsV1[name]
		if !ok {
			return EmptyPostings(), nil
		}
		res := make([]Postings, 0, len(values))
		for _, v := range values {
			postingsOff, ok := e[v]
			if !ok {
				continue
			}
			// Read from the postings table.
			d := encoding.NewDecbufAt(r.b, int(postingsOff), castagnoliTable)
			_, p, err := r.dec.Postings(d.Get())
			if err != nil {
				return nil, errors.Wrap(err, "decode postings")
			}
			res = append(res, p)
		}
		return Merge(res...), nil
	}

	e, ok := r.postings[name]
	if !ok {
		return EmptyPostings(), nil
	}

	if len(values) == 0 {
		return EmptyPostings(), nil
	}

	res := make([]Postings, 0, len(values))
	skip := 0
	valueIndex := 0
	for valueIndex < len(values) && values[valueIndex] < e[0].value {
		// Discard values before the start.
		valueIndex++
	}
	for valueIndex < len(values) {
		value := values[valueIndex]

		i := sort.Search(len(e), func(i int) bool { return e[i].value >= value })
		if i == len(e) {
			// We're past the end.
			break
		}
		if i > 0 && e[i].value != value {
			// Need to look from previous entry.
			i--
		}
		// Don't Crc32 the entire postings offset table, this is very slow
		// so hope any issues were caught at startup.
		d := encoding.NewDecbufAt(r.b, int(r.toc.PostingsTable), nil)
		d.Skip(e[i].off)

		// Iterate on the offset table.
		var postingsOff uint64 // The offset into the postings table.
		for d.Err() == nil {
			if skip == 0 {
				// These are always the same number of bytes,
				// and it's faster to skip than parse.
				skip = d.Len()
				d.Uvarint()      // Keycount.
				d.UvarintBytes() // Label name.
				skip -= d.Len()
			} else {
				d.Skip(skip)
			}
			v := d.UvarintBytes()       // Label value.
			postingsOff = d.Uvarint64() // Offset.
			for string(v) >= value {
				if string(v) == value {
					// Read from the postings table.
					d2 := encoding.NewDecbufAt(r.b, int(postingsOff), castagnoliTable)
					_, p, err := r.dec.Postings(d2.Get())
					if err != nil {
						return nil, errors.Wrap(err, "decode postings")
					}
					res = append(res, p)
				}
				valueIndex++
				if valueIndex == len(values) {
					break
				}
				value = values[valueIndex]
			}
			if i+1 == len(e) || value >= e[i+1].value || valueIndex == len(values) {
				// Need to go to a later postings offset entry, if there is one.
				break
			}
		}
		if d.Err() != nil {
			return nil, errors.Wrap(d.Err(), "get postings offset entry")
		}
	}

	return Merge(res...), nil
}