Golang Key.Equal方法代碼示例

// 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 proto.Key, inclusive bool) (
	rangeCacheKey, *proto.RangeDescriptor) {
	// The cache is indexed using the end-key of the range, but the
	// end-key is non-inclusive by default.
	var metaKey proto.Key
	if !inclusive {
		metaKey = keys.RangeMetaKey(key.Next())
	} else {
		metaKey = keys.RangeMetaKey(key)
	}

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

// ValidateRangeMetaKey validates that the given key is a valid Range Metadata
// key.
func ValidateRangeMetaKey(key proto.Key) error {
	// KeyMin is a valid key.
	if key.Equal(proto.KeyMin) {
		return nil
	}
	// Key must be at least as long as Meta1Prefix.
	if len(key) < len(Meta1Prefix) {
		return NewInvalidRangeMetaKeyError("too short", key)
	}

	prefix, body := proto.Key(key[:len(Meta1Prefix)]), proto.Key(key[len(Meta1Prefix):])

	if prefix.Equal(Meta2Prefix) {
		if body.Less(proto.KeyMax) {
			return nil
		}
		return NewInvalidRangeMetaKeyError("body of meta2 range lookup is >= KeyMax", key)
	}

	if prefix.Equal(Meta1Prefix) {
		if proto.KeyMax.Less(body) {
			return NewInvalidRangeMetaKeyError("body of meta1 range lookup is > KeyMax", key)
		}
		return nil
	}
	return NewInvalidRangeMetaKeyError("not a meta key", key)
}

// Get searches the kv list for 'key' and returns its
// raw byte value if found. ok is true only if the key is found.
func (s *SystemConfig) Get(key proto.Key) ([]byte, bool) {
	l := len(s.Values)
	index := sort.Search(l, func(i int) bool {
		return bytes.Compare(s.Values[i].Key, key) >= 0
	})
	if index == l || !key.Equal(s.Values[index].Key) {
		return nil, false
	}
	// TODO(marc): I'm pretty sure a Value returned by MVCCScan can
	// never be nil. Should check.
	return s.Values[index].Value.Bytes, true
}

// MetaScanBounds returns the start and end keys of the range 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.
func MetaScanBounds(key proto.Key) (proto.Key, proto.Key) {
	if key.Equal(proto.KeyMin) {
		// Special case KeyMin: find the first entry in meta1.
		return Meta1Prefix, Meta1Prefix.PrefixEnd()
	}
	if key.Equal(Meta1KeyMax) {
		// Special case Meta1KeyMax: this is the last key in Meta1, we don't want
		// to start at Next().
		return key, Meta1Prefix.PrefixEnd()
	}
	// Otherwise find the first entry greater than the given key in the same meta prefix.
	return key.Next(), proto.Key(key[:len(Meta1Prefix)]).PrefixEnd()
}

// GetIndex searches the kv list for 'key' and returns its index if found.
func (s *SystemConfig) GetIndex(key proto.Key) (int, bool) {
	if s == nil {
		return 0, false
	}

	l := len(s.Values)
	index := sort.Search(l, func(i int) bool {
		return !s.Values[i].Key.Less(key)
	})
	if index == l || !key.Equal(s.Values[index].Key) {
		return 0, false
	}
	return index, true
}

// ObjectIDForKey returns the object ID (table or database) for 'key',
// or (_, false) if not within the structured key space.
func ObjectIDForKey(key proto.Key) (uint32, bool) {
	if key.Equal(proto.KeyMax) {
		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
}

// ObjectIDForKey returns the object ID (table or database) for 'key',
// or (_, false) if not within the structured key space.
func ObjectIDForKey(key proto.Key) (uint32, bool) {
	if key.Equal(proto.KeyMax) {
		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.
	defer func() {
		// Nothing to do, default return values mean "could not decode", which is
		// definitely the case if DecodeUvarint panics.
		_ = recover()
	}()
	_, id64 := encoding.DecodeUvarint(remaining)
	return uint32(id64), true
}

// 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 proto.Key, isReverse bool) (
	rangeCacheKey, *proto.RangeDescriptor) {
	// The cache is indexed using the end-key of the range, but the
	// end-key is non-inclusive.
	var metaKey proto.Key
	if !isReverse {
		// If it is not reverse scan, we access the cache using key.Next().
		metaKey = keys.RangeMetaKey(key.Next())
	} else {
		// Because reverse scan request is begining at end key(exclusive),so we
		// access the cache using key directly.
		metaKey = keys.RangeMetaKey(key)
	}

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

	// Check that key actually belongs to the range.
	if !rd.ContainsKey(keys.KeyAddress(key)) {
		// The key is the EndKey of the range in reverse scan, just return the range descriptor.
		if isReverse && key.Equal(rd.EndKey) {
			return metaEndKey, rd
		}
		return nil, nil
	}

	// The key is the StartKey of the range in reverse scan. We need to return the previous range
	// descriptor, but it is not in the cache yet.
	if isReverse && key.Equal(rd.StartKey) {
		return nil, nil
	}
	return metaEndKey, rd
}

// 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 proto.Key) (proto.Key, proto.Key, error) {
	if key.Equal(proto.KeyMin) || 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(), 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 ["", "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)], key.Next(), 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.
func MetaScanBounds(key proto.Key) (proto.Key, proto.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(proto.KeyMin) {
		// 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 key, Meta1Prefix.PrefixEnd(), nil
	}
	// Otherwise find the first entry greater than the given key in the same meta prefix.
	return key.Next(), proto.Key(key[:len(Meta1Prefix)]).PrefixEnd(), nil
}