Golang RKey.Equal方法代码示例

// getCachedRangeDescriptorLocked is a helper function to retrieve the
// descriptor of the range which contains the given key, if present in the
// cache. It is assumed that the caller holds a read lock on rdc.rangeCacheMu.
func (rdc *rangeDescriptorCache) getCachedRangeDescriptorLocked(key roachpb.RKey, inclusive bool) (
	rangeCacheKey, *roachpb.RangeDescriptor) {
	// The cache is indexed using the end-key of the range, but the
	// end-key is non-inclusive by default.
	var metaKey roachpb.RKey
	if !inclusive {
		metaKey = meta(key.Next())
	} else {
		metaKey = meta(key)
	}

	k, v, ok := rdc.rangeCache.Ceil(rangeCacheKey(metaKey))
	if !ok {
		return nil, nil
	}
	metaEndKey := k.(rangeCacheKey)
	rd := v.(*roachpb.RangeDescriptor)

	// Check that key actually belongs to the range.
	if !rd.ContainsKey(key) {
		// The key is the EndKey and we're inclusive, so just return the range descriptor.
		if inclusive && key.Equal(rd.EndKey) {
			return metaEndKey, rd
		}
		return nil, nil
	}

	// The key is the StartKey, but we're inclusive and thus need to return the
	// previous range descriptor, but it is not in the cache yet.
	if inclusive && key.Equal(rd.StartKey) {
		return nil, nil
	}
	return metaEndKey, rd
}

// ObjectIDForKey returns the object ID (table or database) for 'key',
// or (_, false) if not within the structured key space.
func ObjectIDForKey(key roachpb.RKey) (uint32, bool) {
	if key.Equal(roachpb.RKeyMax) {
		return 0, false
	}
	if encoding.PeekType(key) != encoding.Int {
		// TODO(marc): this should eventually return SystemDatabaseID.
		return 0, false
	}
	// Consume first encoded int.
	_, id64, err := encoding.DecodeUvarint(key)
	return uint32(id64), err == nil
}

// ObjectIDForKey returns the object ID (table or database) for 'key',
// or (_, false) if not within the structured key space.
func ObjectIDForKey(key roachpb.RKey) (uint32, bool) {
	if key.Equal(roachpb.RKeyMax) {
		return 0, false
	}
	if key.Equal(keys.TableDataPrefix) {
		// TODO(marc): this should eventually return SystemDatabaseID.
		return 0, false
	}
	remaining := bytes.TrimPrefix(key, keys.TableDataPrefix)
	if len(remaining) == len(key) {
		// TrimPrefix returns the input untouched if the prefix doesn't match.
		return 0, false
	}

	// Consume first encoded int.
	_, id64, err := encoding.DecodeUvarint(remaining)
	return uint32(id64), err == nil
}

// validateRangeMetaKey validates that the given key is a valid Range Metadata
// key. This checks only the constraints common to forward and backwards scans:
// correct prefix and not exceeding KeyMax.
func validateRangeMetaKey(key roachpb.RKey) error {
	// KeyMin is a valid key.
	if key.Equal(roachpb.RKeyMin) {
		return nil
	}
	// Key must be at least as long as Meta1Prefix.
	if len(key) < len(Meta1Prefix) {
		return NewInvalidRangeMetaKeyError("too short", key)
	}

	prefix, body := key[:len(Meta1Prefix)], key[len(Meta1Prefix):]
	if !prefix.Equal(Meta2Prefix) && !prefix.Equal(Meta1Prefix) {
		return NewInvalidRangeMetaKeyError("not a meta key", key)
	}

	if roachpb.RKeyMax.Less(body) {
		return NewInvalidRangeMetaKeyError("body of meta key range lookup is > KeyMax", key)
	}
	return nil
}

// MetaScanBounds returns the range [start,end) within which the desired meta
// record can be found by means of an engine scan. The given key must be a
// valid RangeMetaKey as defined by validateRangeMetaKey.
// TODO(tschottdorf): a lot of casting going on inside.
func MetaScanBounds(key roachpb.RKey) (roachpb.Key, roachpb.Key, error) {
	if err := validateRangeMetaKey(key); err != nil {
		return nil, nil, err
	}

	if key.Equal(Meta2KeyMax) {
		return nil, nil, NewInvalidRangeMetaKeyError("Meta2KeyMax can't be used as the key of scan", key)
	}

	if key.Equal(roachpb.RKeyMin) {
		// Special case KeyMin: find the first entry in meta1.
		return Meta1Prefix, Meta1Prefix.PrefixEnd(), nil
	}
	if key.Equal(Meta1KeyMax) {
		// Special case Meta1KeyMax: this is the last key in Meta1, we don't want
		// to start at Next().
		return Meta1KeyMax, Meta1Prefix.PrefixEnd(), nil
	}
	// Otherwise find the first entry greater than the given key in the same meta prefix.
	return key.Next().AsRawKey(), key[:len(Meta1Prefix)].PrefixEnd().AsRawKey(), nil
}

// MetaReverseScanBounds returns the range [start,end) within which the desired
// meta record can be found by means of a reverse engine scan. The given key
// must be a valid RangeMetaKey as defined by validateRangeMetaKey.
func MetaReverseScanBounds(key roachpb.RKey) (roachpb.Key, roachpb.Key, error) {
	if err := validateRangeMetaKey(key); err != nil {
		return nil, nil, err
	}

	if key.Equal(roachpb.RKeyMin) || key.Equal(Meta1Prefix) {
		return nil, nil, NewInvalidRangeMetaKeyError("KeyMin and Meta1Prefix can't be used as the key of reverse scan", key)
	}
	if key.Equal(Meta2Prefix) {
		// Special case Meta2Prefix: this is the first key in Meta2, and the scan
		// interval covers all of Meta1.
		return Meta1Prefix, key.Next().AsRawKey(), nil
	}
	// Otherwise find the first entry greater than the given key and find the last entry
	// in the same prefix. For MVCCReverseScan the endKey is exclusive, if we want to find
	// the range descriptor the given key specified,we need to set the key.Next() as the
	// MVCCReverseScan`s endKey. For example:
	// If we have ranges [a,f) and [f,z), then we'll have corresponding meta records
	// at f and z. If you're looking for the meta record for key f, then you want the
	// second record (exclusive in MVCCReverseScan), hence key.Next() below.
	return key[:len(Meta1Prefix)].AsRawKey(), key.Next().AsRawKey(), nil
}