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schema cache: cache schema version by timestamp #40768

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merged 8 commits into from
Feb 6, 2023
Merged

schema cache: cache schema version by timestamp #40768

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5982d7c
cache schema version by timestamp
hihihuhu Jan 23, 2023
b01a24b
fix test
hihihuhu Jan 25, 2023
611f7e7
avoid recursive locking
hihihuhu Feb 1, 2023
4da7ca7
address comment
hihihuhu Feb 2, 2023
1710996
optimize the code
hihihuhu Feb 2, 2023
3f9ce17
Merge branch 'master' into master
ti-chi-bot Feb 6, 2023
7145ef8
Merge branch 'master' into master
ti-chi-bot Feb 6, 2023
f804d62
Merge branch 'master' into master
ti-chi-bot Feb 6, 2023
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79 changes: 56 additions & 23 deletions infoschema/cache.go
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
package infoschema

import (
"fmt"
"sort"
"sync"

Expand All @@ -36,22 +37,27 @@ var (
// It only promised to cache the infoschema, if it is newer than all the cached.
type InfoCache struct {
mu sync.RWMutex
// cache is sorted by SchemaVersion in descending order
cache []InfoSchema
// record SnapshotTS of the latest schema Insert.
maxUpdatedSnapshotTS uint64
// cache is sorted by both SchemaVersion and timestamp in descending order, assume they have same order
cache []schemaAndTimestamp
}

type schemaAndTimestamp struct {
infoschema InfoSchema
timestamp int64
}

// NewCache creates a new InfoCache.
func NewCache(capacity int) *InfoCache {
return &InfoCache{cache: make([]InfoSchema, 0, capacity)}
return &InfoCache{
cache: make([]schemaAndTimestamp, 0, capacity),
}
}

// Reset resets the cache.
func (h *InfoCache) Reset(capacity int) {
h.mu.Lock()
defer h.mu.Unlock()
h.cache = make([]InfoSchema, 0, capacity)
h.cache = make([]schemaAndTimestamp, 0, capacity)
}

// GetLatest gets the newest information schema.
Expand All @@ -61,18 +67,40 @@ func (h *InfoCache) GetLatest() InfoSchema {
getLatestCounter.Inc()
if len(h.cache) > 0 {
hitLatestCounter.Inc()
return h.cache[0]
return h.cache[0].infoschema
}
return nil
}

// GetSchemaByTimestamp returns the schema used at the specific timestamp
func (h *InfoCache) GetSchemaByTimestamp(ts uint64) (InfoSchema, error) {
h.mu.RLock()
defer h.mu.RUnlock()
return h.getSchemaByTimestampNoLock(ts)
}

func (h *InfoCache) getSchemaByTimestampNoLock(ts uint64) (InfoSchema, error) {
i := sort.Search(len(h.cache), func(i int) bool {
return uint64(h.cache[i].timestamp) <= ts
})
if i < len(h.cache) {
return h.cache[i].infoschema, nil
}

return nil, fmt.Errorf("no schema cached for timestamp %d", ts)
}

// GetByVersion gets the information schema based on schemaVersion. Returns nil if it is not loaded.
func (h *InfoCache) GetByVersion(version int64) InfoSchema {
h.mu.RLock()
defer h.mu.RUnlock()
return h.getByVersionNoLock(version)
}

func (h *InfoCache) getByVersionNoLock(version int64) InfoSchema {
getVersionCounter.Inc()
i := sort.Search(len(h.cache), func(i int) bool {
return h.cache[i].SchemaMetaVersion() <= version
return h.cache[i].infoschema.SchemaMetaVersion() <= version
})

// `GetByVersion` is allowed to load the latest schema that is less than argument `version`.
Expand All @@ -93,9 +121,9 @@ func (h *InfoCache) GetByVersion(version int64) InfoSchema {
// }
// ```

if i < len(h.cache) && (i != 0 || h.cache[i].SchemaMetaVersion() == version) {
if i < len(h.cache) && (i != 0 || h.cache[i].infoschema.SchemaMetaVersion() == version) {
hitVersionCounter.Inc()
return h.cache[i]
return h.cache[i].infoschema
}
return nil
}
Expand All @@ -108,11 +136,9 @@ func (h *InfoCache) GetBySnapshotTS(snapshotTS uint64) InfoSchema {
defer h.mu.RUnlock()

getTSCounter.Inc()
if snapshotTS >= h.maxUpdatedSnapshotTS {
if len(h.cache) > 0 {
hitTSCounter.Inc()
return h.cache[0]
}
if schema, err := h.getSchemaByTimestampNoLock(snapshotTS); err == nil {
hitTSCounter.Inc()
return schema
}
return nil
}
Expand All @@ -125,29 +151,36 @@ func (h *InfoCache) Insert(is InfoSchema, snapshotTS uint64) bool {
defer h.mu.Unlock()

version := is.SchemaMetaVersion()

// assume this is the timestamp order as well
i := sort.Search(len(h.cache), func(i int) bool {
return h.cache[i].SchemaMetaVersion() <= version
return h.cache[i].infoschema.SchemaMetaVersion() <= version
})

if h.maxUpdatedSnapshotTS < snapshotTS {
h.maxUpdatedSnapshotTS = snapshotTS
}

// cached entry
if i < len(h.cache) && h.cache[i].SchemaMetaVersion() == version {
if i < len(h.cache) && h.cache[i].infoschema.SchemaMetaVersion() == version {
if h.cache[i].timestamp > int64(snapshotTS) {
h.cache[i].timestamp = int64(snapshotTS)
}
return true
}

if len(h.cache) < cap(h.cache) {
// has free space, grown the slice
h.cache = h.cache[:len(h.cache)+1]
copy(h.cache[i+1:], h.cache[i:])
h.cache[i] = is
h.cache[i] = schemaAndTimestamp{
infoschema: is,
timestamp: int64(snapshotTS),
}
return true
} else if i < len(h.cache) {
// drop older schema
copy(h.cache[i+1:], h.cache[i:])
h.cache[i] = is
h.cache[i] = schemaAndTimestamp{
infoschema: is,
timestamp: int64(snapshotTS),
}
return true
}
// older than all cached schemas, refuse to cache it
Expand Down
64 changes: 61 additions & 3 deletions infoschema/cache_test.go
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,7 @@ func TestInsert(t *testing.T) {
ic.Insert(is5, 5)
require.Equal(t, is5, ic.GetByVersion(5))
require.Equal(t, is2, ic.GetByVersion(2))
require.Nil(t, ic.GetBySnapshotTS(2))
require.Equal(t, is2, ic.GetBySnapshotTS(2))
require.Equal(t, is5, ic.GetBySnapshotTS(10))

// older
Expand All @@ -59,7 +59,7 @@ func TestInsert(t *testing.T) {
require.Equal(t, is5, ic.GetByVersion(5))
require.Equal(t, is2, ic.GetByVersion(2))
require.Nil(t, ic.GetByVersion(0))
require.Nil(t, ic.GetBySnapshotTS(2))
require.Equal(t, is2, ic.GetBySnapshotTS(2))
require.Equal(t, is6, ic.GetBySnapshotTS(10))

// replace 2, drop 2
Expand Down Expand Up @@ -91,7 +91,7 @@ func TestInsert(t *testing.T) {
require.Nil(t, ic.GetByVersion(2))
require.Nil(t, ic.GetByVersion(0))
require.Nil(t, ic.GetBySnapshotTS(2))
require.Nil(t, ic.GetBySnapshotTS(5))
require.Equal(t, is5, ic.GetBySnapshotTS(5))
require.Equal(t, is6, ic.GetBySnapshotTS(10))
}

Expand Down Expand Up @@ -129,3 +129,61 @@ func TestGetLatest(t *testing.T) {
ic.Insert(is0, 0)
require.Equal(t, is2, ic.GetLatest())
}

func TestGetByTimestamp(t *testing.T) {
ic := infoschema.NewCache(16)
require.NotNil(t, ic)
require.Nil(t, ic.GetLatest())

is1 := infoschema.MockInfoSchemaWithSchemaVer(nil, 1)
ic.Insert(is1, 1)
require.Equal(t, is1, ic.GetLatest())
_, err := ic.GetSchemaByTimestamp(0)
require.NotNil(t, err)
schema, err := ic.GetSchemaByTimestamp(1)
require.Nil(t, err)
require.Equal(t, int64(1), schema.SchemaMetaVersion())
require.Equal(t, is1, ic.GetBySnapshotTS(1))
schema, err = ic.GetSchemaByTimestamp(2)
require.Nil(t, err)
require.Equal(t, int64(1), schema.SchemaMetaVersion())
require.Equal(t, is1, ic.GetBySnapshotTS(2))

is2 := infoschema.MockInfoSchemaWithSchemaVer(nil, 2)
ic.Insert(is2, 2)
require.Equal(t, is2, ic.GetLatest())
_, err = ic.GetSchemaByTimestamp(0)
require.NotNil(t, err)
schema, err = ic.GetSchemaByTimestamp(1)
require.Nil(t, err)
require.Equal(t, int64(1), schema.SchemaMetaVersion())
require.Equal(t, is1, ic.GetBySnapshotTS(1))
schema, err = ic.GetSchemaByTimestamp(2)
require.Nil(t, err)
require.Equal(t, int64(2), schema.SchemaMetaVersion())
require.Equal(t, is2, ic.GetBySnapshotTS(2))
schema, err = ic.GetSchemaByTimestamp(3)
require.Nil(t, err)
require.Equal(t, int64(2), schema.SchemaMetaVersion())
require.Equal(t, is2, ic.GetBySnapshotTS(3))

is0 := infoschema.MockInfoSchemaWithSchemaVer(nil, 0)
ic.Insert(is0, 0)
require.Equal(t, is2, ic.GetLatest())
schema, err = ic.GetSchemaByTimestamp(0)
require.Nil(t, err)
require.Equal(t, int64(0), schema.SchemaMetaVersion())
require.Equal(t, is0, ic.GetBySnapshotTS(0))
schema, err = ic.GetSchemaByTimestamp(1)
require.Nil(t, err)
require.Equal(t, int64(1), schema.SchemaMetaVersion())
require.Equal(t, is1, ic.GetBySnapshotTS(1))
schema, err = ic.GetSchemaByTimestamp(2)
require.Nil(t, err)
require.Equal(t, int64(2), schema.SchemaMetaVersion())
require.Equal(t, is2, ic.GetBySnapshotTS(2))
schema, err = ic.GetSchemaByTimestamp(3)
require.Nil(t, err)
require.Equal(t, int64(2), schema.SchemaMetaVersion())
require.Equal(t, is2, ic.GetBySnapshotTS(3))
}