storage: initial key index
Xiang Li
parent
1a9dcd2f72
commit
32d44aa3b2
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@ -0,0 +1,200 @@
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package storage
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import (
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"bytes"
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"errors"
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"log"
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"github.com/google/btree"
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)
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var (
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ErrIndexNotFound = errors.New("index: not found")
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)
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// keyIndex stores the index of an key in the backend.
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// Each keyIndex has at least one key generation.
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// Each generation might have several key versions.
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// Tombstone on a key appends an tombstone version at the end
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// of the current generation and creates a new empty generation.
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// Each version of a key has an index pointing to the backend.
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//
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// For example: put(1);put(2);tombstone(3);put(4);tombstone(5) on key "foo"
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// generate a keyIndex:
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// key: "foo"
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// index: 5
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// generations:
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// {empty}
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// {4, 5(t)}
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// {1, 2, 3(t)}
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//
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// Compact a keyIndex removes the versions with smaller or equal to
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// index except the largest one. If the generations becomes empty
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// during compaction, it will be removed. if all the generations get
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// removed, the keyIndex Should be removed.
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// For example:
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// compact(2) on the previous example
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// generations:
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// {empty}
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// {4, 5(t)}
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// {2, 3(t)}
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//
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// compact(4)
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// generations:
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// {empty}
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// {4, 5(t)}
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//
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// compact(5):
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// generations:
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// {empty}
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// {5(t)}
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//
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// compact(6):
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// generations:
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// {empty} -> key SHOULD be removed.
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type keyIndex struct {
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key []byte
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index uint64
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generations []generation
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}
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// put puts an index to the keyIndex.
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func (ki *keyIndex) put(index uint64) {
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if index < ki.index {
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log.Panicf("store.keyindex: put with unexpected smaller index [%d / %d]", index, ki.index)
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}
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if len(ki.generations) == 0 {
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ki.generations = append(ki.generations, generation{})
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}
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g := &ki.generations[len(ki.generations)-1]
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g.cont = append(g.cont, index)
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g.ver++
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ki.index = index
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}
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// tombstone puts an index, pointing to a tombstone, to the keyIndex.
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// It also creates a new empty generation in the keyIndex.
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func (ki *keyIndex) tombstone(index uint64) {
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if ki.isEmpty() {
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log.Panicf("store.keyindex: unexpected tombstone on empty keyIndex %s", string(ki.key))
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}
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ki.put(index)
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ki.generations = append(ki.generations, generation{})
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}
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// get gets the index of thk that satisfies the given atIndex.
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// Index must be lower or equal to the given atIndex.
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func (ki *keyIndex) get(atIndex uint64) (index uint64, err error) {
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if ki.isEmpty() {
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log.Panicf("store.keyindex: unexpected get on empty keyIndex %s", string(ki.key))
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}
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g := ki.findGeneration(atIndex)
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if g.isEmpty() {
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return 0, ErrIndexNotFound
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}
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f := func(index, ver uint64) bool {
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if index <= atIndex {
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return false
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}
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return true
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}
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_, n := g.walk(f)
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if n != -1 {
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return g.cont[n], nil
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}
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return 0, ErrIndexNotFound
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}
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// compact compacts a keyIndex by removing the versions with smaller or equal
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// index than the given atIndex except the largest one.
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// If a generation becomes empty during compaction, it will be removed.
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func (ki *keyIndex) compact(atIndex uint64, available map[uint64]struct{}) {
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if ki.isEmpty() {
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log.Panic("store.keyindex: unexpected compact on empty keyIndex %s", string(ki.key))
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}
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// walk until reaching the first content that has an index smaller or equal to
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// the atIndex.
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// add all the reached indexes into available map.
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f := func(index, _ uint64) bool {
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available[index] = struct{}{}
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if index <= atIndex {
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return false
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}
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return true
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}
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g := ki.findGeneration(atIndex)
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i := len(ki.generations) - 1
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for i >= 0 {
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wg := &ki.generations[i]
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if wg == g {
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break
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}
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wg.walk(f)
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i--
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}
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_, n := g.walk(f)
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// remove the previous contents.
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if n != -1 {
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g.cont = g.cont[n:]
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}
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// remove the previous generations.
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ki.generations = ki.generations[i:]
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return
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}
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func (ki *keyIndex) isEmpty() bool {
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return len(ki.generations) == 1 && ki.generations[0].isEmpty()
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}
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// findGeneartion finds out the generation of the keyIndex that the
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// given index belongs to.
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func (ki *keyIndex) findGeneration(index uint64) *generation {
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g, youngerg := len(ki.generations)-1, len(ki.generations)-2
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// If the head index of a younger generation is smaller than
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// the given index, the index cannot be in the younger
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// generation.
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for youngerg >= 0 && ki.generations[youngerg].cont != nil {
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yg := ki.generations[youngerg]
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if yg.cont[len(yg.cont)-1] < index {
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break
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}
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g--
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youngerg--
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}
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if g < 0 {
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return nil
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}
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return &ki.generations[g]
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}
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func (a *keyIndex) Less(b btree.Item) bool {
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return bytes.Compare(a.key, b.(*keyIndex).key) == -1
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}
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type generation struct {
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ver uint64
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cont []uint64
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}
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func (g *generation) isEmpty() bool { return len(g.cont) == 0 }
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func (g *generation) walk(f func(index, ver uint64) bool) (uint64, int) {
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ver := g.ver
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l := len(g.cont)
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for i := range g.cont {
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ok := f(g.cont[l-i-1], ver)
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if !ok {
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return ver, l - i - 1
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}
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ver--
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}
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return 0, -1
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}
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@ -0,0 +1,364 @@
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package storage
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import (
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"reflect"
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"testing"
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)
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func TestKeyIndexGet(t *testing.T) {
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// key: "foo"
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// index: 12
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// generations:
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// {empty}
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// {8[1], 10[2], 12(t)[3]}
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// {4[2], 6(t)[3]}
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ki := newTestKeyIndex()
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ki.compact(4, make(map[uint64]struct{}))
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tests := []struct {
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index uint64
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windex uint64
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werr error
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}{
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// expected not exist on an index that is greater than the last tombstone
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{13, 0, ErrIndexNotFound},
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{13, 0, ErrIndexNotFound},
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// get on generation 2
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{12, 12, nil},
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{11, 10, nil},
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{10, 10, nil},
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{9, 8, nil},
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{8, 8, nil},
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{7, 0, ErrIndexNotFound},
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// get on generation 1
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{6, 6, nil},
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{5, 4, nil},
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{4, 4, nil},
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}
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for i, tt := range tests {
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index, err := ki.get(tt.index)
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if err != tt.werr {
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t.Errorf("#%d: err = %v, want %v", i, err, tt.werr)
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}
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if index != tt.windex {
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t.Errorf("#%d: index = %d, want %d", i, index, tt.index)
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}
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}
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}
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func TestKeyIndexPut(t *testing.T) {
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ki := &keyIndex{key: []byte("foo")}
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ki.put(5)
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wki := &keyIndex{
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key: []byte("foo"),
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index: 5,
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generations: []generation{{ver: 1, cont: []uint64{5}}},
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}
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if !reflect.DeepEqual(ki, wki) {
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t.Errorf("ki = %+v, want %+v", ki, wki)
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}
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ki.put(7)
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wki = &keyIndex{
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key: []byte("foo"),
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index: 7,
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generations: []generation{{ver: 2, cont: []uint64{5, 7}}},
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}
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if !reflect.DeepEqual(ki, wki) {
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t.Errorf("ki = %+v, want %+v", ki, wki)
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}
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}
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func TestKeyIndexTombstone(t *testing.T) {
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ki := &keyIndex{key: []byte("foo")}
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ki.put(5)
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ki.tombstone(7)
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wki := &keyIndex{
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key: []byte("foo"),
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index: 7,
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generations: []generation{{ver: 2, cont: []uint64{5, 7}}, {}},
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}
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if !reflect.DeepEqual(ki, wki) {
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t.Errorf("ki = %+v, want %+v", ki, wki)
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}
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ki.put(8)
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ki.put(9)
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ki.tombstone(15)
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wki = &keyIndex{
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key: []byte("foo"),
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index: 15,
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generations: []generation{{ver: 2, cont: []uint64{5, 7}}, {ver: 3, cont: []uint64{8, 9, 15}}, {}},
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}
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if !reflect.DeepEqual(ki, wki) {
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t.Errorf("ki = %+v, want %+v", ki, wki)
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}
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}
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func TestKeyIndexCompact(t *testing.T) {
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tests := []struct {
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compact uint64
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wki *keyIndex
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wam map[uint64]struct{}
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}{
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{
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1,
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&keyIndex{
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key: []byte("foo"),
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index: 12,
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generations: []generation{
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{ver: 3, cont: []uint64{2, 4, 6}},
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{ver: 3, cont: []uint64{8, 10, 12}},
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{},
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},
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},
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map[uint64]struct{}{
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2: struct{}{}, 4: struct{}{}, 6: struct{}{},
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8: struct{}{}, 10: struct{}{}, 12: struct{}{},
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},
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},
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{
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2,
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&keyIndex{
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key: []byte("foo"),
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index: 12,
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generations: []generation{
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{ver: 3, cont: []uint64{2, 4, 6}},
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{ver: 3, cont: []uint64{8, 10, 12}},
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{},
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},
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},
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map[uint64]struct{}{
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2: struct{}{}, 4: struct{}{}, 6: struct{}{},
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8: struct{}{}, 10: struct{}{}, 12: struct{}{},
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},
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},
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{
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3,
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&keyIndex{
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key: []byte("foo"),
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index: 12,
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generations: []generation{
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{ver: 3, cont: []uint64{2, 4, 6}},
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{ver: 3, cont: []uint64{8, 10, 12}},
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{},
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},
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},
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map[uint64]struct{}{
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2: struct{}{}, 4: struct{}{}, 6: struct{}{},
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8: struct{}{}, 10: struct{}{}, 12: struct{}{},
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},
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},
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{
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4,
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&keyIndex{
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key: []byte("foo"),
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index: 12,
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generations: []generation{
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{ver: 3, cont: []uint64{4, 6}},
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{ver: 3, cont: []uint64{8, 10, 12}},
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{},
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},
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},
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map[uint64]struct{}{
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4: struct{}{}, 6: struct{}{},
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8: struct{}{}, 10: struct{}{}, 12: struct{}{},
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},
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},
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{
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5,
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&keyIndex{
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key: []byte("foo"),
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index: 12,
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generations: []generation{
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{ver: 3, cont: []uint64{4, 6}},
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{ver: 3, cont: []uint64{8, 10, 12}},
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{},
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},
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},
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map[uint64]struct{}{
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4: struct{}{}, 6: struct{}{},
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8: struct{}{}, 10: struct{}{}, 12: struct{}{},
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},
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},
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{
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6,
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&keyIndex{
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key: []byte("foo"),
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index: 12,
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generations: []generation{
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{ver: 3, cont: []uint64{6}},
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{ver: 3, cont: []uint64{8, 10, 12}},
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{},
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},
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},
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map[uint64]struct{}{
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6: struct{}{},
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8: struct{}{}, 10: struct{}{}, 12: struct{}{},
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},
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},
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{
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7,
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&keyIndex{
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key: []byte("foo"),
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index: 12,
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generations: []generation{
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{ver: 3, cont: []uint64{8, 10, 12}},
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{},
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},
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},
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map[uint64]struct{}{
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8: struct{}{}, 10: struct{}{}, 12: struct{}{},
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},
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},
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{
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8,
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&keyIndex{
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key: []byte("foo"),
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index: 12,
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generations: []generation{
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{ver: 3, cont: []uint64{8, 10, 12}},
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{},
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},
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},
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map[uint64]struct{}{
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8: struct{}{}, 10: struct{}{}, 12: struct{}{},
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},
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},
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{
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9,
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&keyIndex{
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key: []byte("foo"),
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index: 12,
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generations: []generation{
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{ver: 3, cont: []uint64{8, 10, 12}},
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{},
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},
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},
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map[uint64]struct{}{
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8: struct{}{}, 10: struct{}{}, 12: struct{}{},
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},
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},
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{
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10,
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&keyIndex{
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key: []byte("foo"),
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index: 12,
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generations: []generation{
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{ver: 3, cont: []uint64{10, 12}},
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{},
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},
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},
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map[uint64]struct{}{
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10: struct{}{}, 12: struct{}{},
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},
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},
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{
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11,
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&keyIndex{
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key: []byte("foo"),
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index: 12,
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generations: []generation{
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{ver: 3, cont: []uint64{10, 12}},
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{},
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},
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},
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map[uint64]struct{}{
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10: struct{}{}, 12: struct{}{},
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},
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},
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{
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12,
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&keyIndex{
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key: []byte("foo"),
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index: 12,
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generations: []generation{
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{ver: 3, cont: []uint64{12}},
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{},
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},
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},
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map[uint64]struct{}{
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12: struct{}{},
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},
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},
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{
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13,
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&keyIndex{
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key: []byte("foo"),
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index: 12,
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generations: []generation{
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{},
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},
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},
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map[uint64]struct{}{},
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},
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}
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// Continous Compaction
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ki := newTestKeyIndex()
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for i, tt := range tests {
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am := make(map[uint64]struct{})
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ki.compact(tt.compact, am)
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if !reflect.DeepEqual(ki, tt.wki) {
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t.Errorf("#%d: ki = %+v, want %+v", i, ki, tt.wki)
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}
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if !reflect.DeepEqual(am, tt.wam) {
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t.Errorf("#%d: am = %+v, want %+v", am, tt.wam)
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}
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}
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// Jump Compaction
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for i, tt := range tests {
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if (i%2 == 0 && i < 6) && (i%2 == 1 && i > 6) {
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am := make(map[uint64]struct{})
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ki.compact(tt.compact, am)
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if !reflect.DeepEqual(ki, tt.wki) {
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t.Errorf("#%d: ki = %+v, want %+v", i, ki, tt.wki)
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}
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if !reflect.DeepEqual(am, tt.wam) {
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t.Errorf("#%d: am = %+v, want %+v", am, tt.wam)
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}
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}
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}
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// OnceCompaction
|
||||
for i, tt := range tests {
|
||||
ki := newTestKeyIndex()
|
||||
am := make(map[uint64]struct{})
|
||||
ki.compact(tt.compact, am)
|
||||
if !reflect.DeepEqual(ki, tt.wki) {
|
||||
t.Errorf("#%d: ki = %+v, want %+v", i, ki, tt.wki)
|
||||
}
|
||||
if !reflect.DeepEqual(am, tt.wam) {
|
||||
t.Errorf("#%d: am = %+v, want %+v", am, tt.wam)
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
func newTestKeyIndex() *keyIndex {
|
||||
// key: "foo"
|
||||
// index: 12
|
||||
// generations:
|
||||
// {empty}
|
||||
// {8[1], 10[2], 12(t)[3]}
|
||||
// {2[1], 4[2], 6(t)[3]}
|
||||
|
||||
ki := &keyIndex{key: []byte("foo")}
|
||||
ki.put(2)
|
||||
ki.put(4)
|
||||
ki.tombstone(6)
|
||||
ki.put(8)
|
||||
ki.put(10)
|
||||
ki.tombstone(12)
|
||||
return ki
|
||||
}
|
||||
Loading…
Reference in New Issue