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gitea/vendor/github.com/pingcap/tidb/kv/index_iter.go

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// Copyright 2015 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package kv
import (
"bytes"
"encoding/binary"
"io"
"github.com/juju/errors"
"github.com/pingcap/tidb/util/codec"
"github.com/pingcap/tidb/util/types"
)
var (
_ Index = (*kvIndex)(nil)
_ IndexIterator = (*indexIter)(nil)
)
// IndexIterator is the interface for iterator of index data on KV store.
type IndexIterator interface {
Next() (k []types.Datum, h int64, err error)
Close()
}
// Index is the interface for index data on KV store.
type Index interface {
// Create supports insert into statement.
Create(rm RetrieverMutator, indexedValues []types.Datum, h int64) error
// Delete supports delete from statement.
Delete(m Mutator, indexedValues []types.Datum, h int64) error
// Drop supports drop table, drop index statements.
Drop(rm RetrieverMutator) error
// Exist supports check index exists or not.
Exist(rm RetrieverMutator, indexedValues []types.Datum, h int64) (bool, int64, error)
// GenIndexKey generates an index key.
GenIndexKey(indexedValues []types.Datum, h int64) (key []byte, distinct bool, err error)
// Seek supports where clause.
Seek(r Retriever, indexedValues []types.Datum) (iter IndexIterator, hit bool, err error)
// SeekFirst supports aggregate min and ascend order by.
SeekFirst(r Retriever) (iter IndexIterator, err error)
}
func encodeHandle(h int64) []byte {
buf := &bytes.Buffer{}
err := binary.Write(buf, binary.BigEndian, h)
if err != nil {
panic(err)
}
return buf.Bytes()
}
func decodeHandle(data []byte) (int64, error) {
var h int64
buf := bytes.NewBuffer(data)
err := binary.Read(buf, binary.BigEndian, &h)
return h, errors.Trace(err)
}
// indexIter is for KV store index iterator.
type indexIter struct {
it Iterator
idx *kvIndex
prefix Key
}
// Close does the clean up works when KV store index iterator is closed.
func (c *indexIter) Close() {
if c.it != nil {
c.it.Close()
c.it = nil
}
}
// Next returns current key and moves iterator to the next step.
func (c *indexIter) Next() (val []types.Datum, h int64, err error) {
if !c.it.Valid() {
return nil, 0, errors.Trace(io.EOF)
}
if !c.it.Key().HasPrefix(c.prefix) {
return nil, 0, errors.Trace(io.EOF)
}
// get indexedValues
buf := c.it.Key()[len(c.prefix):]
vv, err := codec.Decode(buf)
if err != nil {
return nil, 0, errors.Trace(err)
}
// if index is *not* unique, the handle is in keybuf
if !c.idx.unique {
h = vv[len(vv)-1].GetInt64()
val = vv[0 : len(vv)-1]
} else {
// otherwise handle is value
h, err = decodeHandle(c.it.Value())
if err != nil {
return nil, 0, errors.Trace(err)
}
val = vv
}
// update new iter to next
err = c.it.Next()
if err != nil {
return nil, 0, errors.Trace(err)
}
return
}
// kvIndex is the data structure for index data in the KV store.
type kvIndex struct {
indexName string
indexID int64
unique bool
prefix Key
}
// GenIndexPrefix generates the index prefix.
func GenIndexPrefix(indexPrefix Key, indexID int64) Key {
buf := make([]byte, 0, len(indexPrefix)+8)
buf = append(buf, indexPrefix...)
buf = codec.EncodeInt(buf, indexID)
return buf
}
// NewKVIndex builds a new kvIndex object.
func NewKVIndex(indexPrefix Key, indexName string, indexID int64, unique bool) Index {
index := &kvIndex{
indexName: indexName,
indexID: indexID,
unique: unique,
prefix: GenIndexPrefix(indexPrefix, indexID),
}
return index
}
// GenIndexKey generates storage key for index values. Returned distinct indicates whether the
// indexed values should be distinct in storage (i.e. whether handle is encoded in the key).
func (c *kvIndex) GenIndexKey(indexedValues []types.Datum, h int64) (key []byte, distinct bool, err error) {
if c.unique {
// See: https://dev.mysql.com/doc/refman/5.7/en/create-index.html
// A UNIQUE index creates a constraint such that all values in the index must be distinct.
// An error occurs if you try to add a new row with a key value that matches an existing row.
// For all engines, a UNIQUE index permits multiple NULL values for columns that can contain NULL.
distinct = true
for _, cv := range indexedValues {
if cv.Kind() == types.KindNull {
distinct = false
break
}
}
}
key = append(key, c.prefix...)
if distinct {
key, err = codec.EncodeKey(key, indexedValues...)
} else {
key, err = codec.EncodeKey(key, append(indexedValues, types.NewDatum(h))...)
}
if err != nil {
return nil, false, errors.Trace(err)
}
return
}
// Create creates a new entry in the kvIndex data.
// If the index is unique and there is an existing entry with the same key, Create will return ErrKeyExists.
func (c *kvIndex) Create(rm RetrieverMutator, indexedValues []types.Datum, h int64) error {
key, distinct, err := c.GenIndexKey(indexedValues, h)
if err != nil {
return errors.Trace(err)
}
if !distinct {
// TODO: reconsider value
err = rm.Set(key, []byte("timestamp?"))
return errors.Trace(err)
}
_, err = rm.Get(key)
if IsErrNotFound(err) {
err = rm.Set(key, encodeHandle(h))
return errors.Trace(err)
}
return errors.Trace(ErrKeyExists)
}
// Delete removes the entry for handle h and indexdValues from KV index.
func (c *kvIndex) Delete(m Mutator, indexedValues []types.Datum, h int64) error {
key, _, err := c.GenIndexKey(indexedValues, h)
if err != nil {
return errors.Trace(err)
}
err = m.Delete(key)
return errors.Trace(err)
}
// Drop removes the KV index from store.
func (c *kvIndex) Drop(rm RetrieverMutator) error {
it, err := rm.Seek(c.prefix)
if err != nil {
return errors.Trace(err)
}
defer it.Close()
// remove all indices
for it.Valid() {
if !it.Key().HasPrefix(c.prefix) {
break
}
err := rm.Delete(it.Key())
if err != nil {
return errors.Trace(err)
}
err = it.Next()
if err != nil {
return errors.Trace(err)
}
}
return nil
}
// Seek searches KV index for the entry with indexedValues.
func (c *kvIndex) Seek(r Retriever, indexedValues []types.Datum) (iter IndexIterator, hit bool, err error) {
key, _, err := c.GenIndexKey(indexedValues, 0)
if err != nil {
return nil, false, errors.Trace(err)
}
it, err := r.Seek(key)
if err != nil {
return nil, false, errors.Trace(err)
}
// check if hit
hit = false
if it.Valid() && it.Key().Cmp(key) == 0 {
hit = true
}
return &indexIter{it: it, idx: c, prefix: c.prefix}, hit, nil
}
// SeekFirst returns an iterator which points to the first entry of the KV index.
func (c *kvIndex) SeekFirst(r Retriever) (iter IndexIterator, err error) {
it, err := r.Seek(c.prefix)
if err != nil {
return nil, errors.Trace(err)
}
return &indexIter{it: it, idx: c, prefix: c.prefix}, nil
}
func (c *kvIndex) Exist(rm RetrieverMutator, indexedValues []types.Datum, h int64) (bool, int64, error) {
key, distinct, err := c.GenIndexKey(indexedValues, h)
if err != nil {
return false, 0, errors.Trace(err)
}
value, err := rm.Get(key)
if IsErrNotFound(err) {
return false, 0, nil
}
if err != nil {
return false, 0, errors.Trace(err)
}
// For distinct index, the value of key is handle.
if distinct {
handle, err := decodeHandle(value)
if err != nil {
return false, 0, errors.Trace(err)
}
if handle != h {
return true, handle, errors.Trace(ErrKeyExists)
}
return true, handle, nil
}
return true, h, nil
}