示例#1
0
// DecodeIndexKeyPrefix decodes the prefix of an index key and returns the
// index id and a slice for the rest of the key.
//
// Don't use this function in the scan "hot path".
func DecodeIndexKeyPrefix(a *DatumAlloc, desc *TableDescriptor, key []byte) (
	indexID IndexID, remaining []byte, err error,
) {
	// TODO(dan): This whole operation is n^2 because of the interleaves
	// bookkeeping. We could improve it to n with a prefix tree of components.

	interleaves := append([]IndexDescriptor{desc.PrimaryIndex}, desc.Indexes...)

	for component := 0; ; component++ {
		var tableID ID
		key, tableID, indexID, err = DecodeTableIDIndexID(key)
		if err != nil {
			return 0, nil, err
		}
		if tableID == desc.ID {
			// Once desc's table id has been decoded, there can be no more
			// interleaves.
			remaining = key
			break
		}

		for i := len(interleaves) - 1; i >= 0; i-- {
			if len(interleaves[i].Interleave.Ancestors) <= component ||
				interleaves[i].Interleave.Ancestors[component].TableID != tableID ||
				interleaves[i].Interleave.Ancestors[component].IndexID != indexID {

				// This component, and thus this interleave, doesn't match what was
				// decoded, remove it.
				copy(interleaves[i:], interleaves[i+1:])
				interleaves = interleaves[:len(interleaves)-1]
			}
		}
		// The decoded key doesn't many any known interleaves
		if len(interleaves) == 0 {
			return 0, nil, errors.Errorf("no known interleaves for key")
		}

		// Anything left has the same SharedPrefixLen at index `component`, so just
		// use the first one.
		for i := uint32(0); i < interleaves[0].Interleave.Ancestors[component].SharedPrefixLen; i++ {
			l, err := encoding.PeekLength(key)
			if err != nil {
				return 0, nil, err
			}
			key = key[l:]
		}

		// We reuse NotNullDescending as the interleave sentinel, consume it.
		var ok bool
		key, ok = encoding.DecodeIfNotNull(key)
		if !ok {
			return 0, nil, errors.Errorf("invalid interleave key")
		}
	}

	return indexID, key, err
}
示例#2
0
// SetFromBuffer initializes the EncDatum with an encoding that is possibly
// followed by other data. Similar to SetEncoded, except that this function
// figures out where the encoding stops and returns a slice for the rest of the
// buffer.
func (ed *EncDatum) SetFromBuffer(
	typ ColumnType_Kind, enc DatumEncoding, buf []byte,
) (remaining []byte, err error) {
	var encLen int
	switch enc {
	case DatumEncoding_ASCENDING_KEY, DatumEncoding_DESCENDING_KEY:
		encLen, err = encoding.PeekLength(buf)
	case DatumEncoding_VALUE:
		encLen, err = roachpb.PeekValueLength(buf)
	default:
		panic(fmt.Sprintf("unknown encoding %s", ed.encoding))
	}
	if err != nil {
		return nil, err
	}
	ed.SetEncoded(typ, enc, buf[:encLen])
	return buf[encLen:], nil
}