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rowcache.go
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rowcache.go
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// Copyright 2012, Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package tabletserver
import (
"encoding/binary"
"strconv"
"time"
"github.com/youtube/vitess/go/sqltypes"
"github.com/youtube/vitess/go/stats"
"github.com/youtube/vitess/go/vt/proto/vtrpc"
"github.com/youtube/vitess/go/vt/schema"
"golang.org/x/net/context"
)
var cacheStats = stats.NewTimings("Rowcache")
var pack = binary.BigEndian
const (
rcDeleted = 1
// maxKeyLen is a value less than memcache's limit of 250.
maxKeyLen = 200
// maxDataLen prevents large rows from being inserted in rowcache.
maxDataLen = 8000
)
// RowCache gives a table-level view into the rowcache.
type RowCache struct {
tableInfo *TableInfo
prefix string
cachePool *CachePool
}
// RCResult represents the result of a cache multi-fetch.
type RCResult struct {
Row []sqltypes.Value
Cas uint64
}
// NewRowCache creates a new RowCache.
func NewRowCache(tableInfo *TableInfo, cachePool *CachePool) *RowCache {
prefix := strconv.FormatInt(cachePool.maxPrefix.Add(1), 36) + "."
return &RowCache{tableInfo, prefix, cachePool}
}
// Get fetches the values for the specified keys.
func (rc *RowCache) Get(ctx context.Context, keys []string) (results map[string]RCResult) {
mkeys := make([]string, 0, len(keys))
for _, key := range keys {
if len(key) > maxKeyLen {
continue
}
mkeys = append(mkeys, rc.prefix+key)
}
prefixlen := len(rc.prefix)
conn := rc.cachePool.Get(ctx)
// This is not the same as defer rc.cachePool.Put(conn)
defer func() { rc.cachePool.Put(conn) }()
defer cacheStats.Record("Exec", time.Now())
mcresults, err := conn.Gets(mkeys...)
if err != nil {
conn.Close()
conn = nil
panic(NewTabletError(ErrFatal, vtrpc.ErrorCode_INTERNAL_ERROR, "%s", err))
}
results = make(map[string]RCResult, len(mkeys))
for _, mcresult := range mcresults {
if mcresult.Flags == rcDeleted {
// The row was recently invalidated.
// If the caller reads the row from db, they can update it
// back as long as it's not updated again.
results[mcresult.Key[prefixlen:]] = RCResult{Cas: mcresult.Cas}
continue
}
row := rc.decodeRow(mcresult.Value)
if row == nil {
panic(NewTabletError(ErrFatal, vtrpc.ErrorCode_INTERNAL_ERROR, "Corrupt data for %s", mcresult.Key))
}
results[mcresult.Key[prefixlen:]] = RCResult{Row: row, Cas: mcresult.Cas}
}
return
}
// Set pushes the specified row into the rowcache.
func (rc *RowCache) Set(ctx context.Context, key string, row []sqltypes.Value, cas uint64) {
if len(key) > maxKeyLen {
return
}
b := rc.encodeRow(row)
if b == nil {
return
}
conn := rc.cachePool.Get(ctx)
defer func() { rc.cachePool.Put(conn) }()
mkey := rc.prefix + key
var err error
if cas == 0 {
// Either caller didn't find the value at all
// or they didn't look for it in the first place.
_, err = conn.Add(mkey, 0, 0, b)
} else {
// Caller is trying to update a row that recently changed.
_, err = conn.Cas(mkey, 0, 0, b, cas)
}
if err != nil {
conn.Close()
conn = nil
panic(NewTabletError(ErrFatal, vtrpc.ErrorCode_INTERNAL_ERROR, "%s", err))
}
}
// Delete marks the row as deleted.
func (rc *RowCache) Delete(ctx context.Context, key string) {
if len(key) > maxKeyLen {
return
}
conn := rc.cachePool.Get(ctx)
defer func() { rc.cachePool.Put(conn) }()
mkey := rc.prefix + key
_, err := conn.Set(mkey, rcDeleted, 0, nil)
if err != nil {
conn.Close()
conn = nil
panic(NewTabletError(ErrFatal, vtrpc.ErrorCode_INTERNAL_ERROR, "%s", err))
}
}
func (rc *RowCache) encodeRow(row []sqltypes.Value) (b []byte) {
length := 0
for _, v := range row {
length += len(v.Raw())
if length > maxDataLen {
return nil
}
}
datastart := 4 + len(row)*4
b = make([]byte, datastart+length)
data := b[datastart:datastart]
pack.PutUint32(b, uint32(len(row)))
for i, v := range row {
if v.IsNull() {
pack.PutUint32(b[4+i*4:], 0xFFFFFFFF)
continue
}
data = append(data, v.Raw()...)
pack.PutUint32(b[4+i*4:], uint32(len(v.Raw())))
}
return b
}
func (rc *RowCache) decodeRow(b []byte) (row []sqltypes.Value) {
rowlen := pack.Uint32(b)
data := b[4+rowlen*4:]
row = make([]sqltypes.Value, rowlen)
for i := range row {
length := pack.Uint32(b[4+i*4:])
if length == 0xFFFFFFFF {
continue
}
if length > uint32(len(data)) {
// Corrupt data
return nil
}
if rc.tableInfo.Columns[i].Category == schema.CAT_NUMBER {
row[i] = sqltypes.MakeNumeric(data[:length])
} else {
row[i] = sqltypes.MakeString(data[:length])
}
data = data[length:]
}
return row
}