*: remove non-prepared plan cache (pingcap#7040)

* *: remove non-prepared plan cache non-prepared plan cache is not usable if we can only do full string match. And further development doesn't worth the effort.
icditwang · Jul 13, 2018 · 63c4562 · 63c4562
1 parent 34d8fd8
commit 63c4562
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Showing 10 changed files with 29 additions and 263 deletions.
diff --git a/config/config.go b/config/config.go
@@ -62,7 +62,6 @@ type Config struct {
 	Status            Status            `toml:"status" json:"status"`
 	Performance       Performance       `toml:"performance" json:"performance"`
 	XProtocol         XProtocol         `toml:"xprotocol" json:"xprotocol"`
-	PlanCache         PlanCache         `toml:"plan-cache" json:"plan-cache"`
 	PreparedPlanCache PreparedPlanCache `toml:"prepared-plan-cache" json:"prepared-plan-cache"`
 	OpenTracing       OpenTracing       `toml:"opentracing" json:"opentracing"`
 	ProxyProtocol     ProxyProtocol     `toml:"proxy-protocol" json:"proxy-protocol"`
@@ -287,11 +286,6 @@ var defaultConf = Config{
 		Networks:      "",
 		HeaderTimeout: 5,
 	},
-	PlanCache: PlanCache{
-		Enabled:  false,
-		Capacity: 2560,
-		Shards:   256,
-	},
 	PreparedPlanCache: PreparedPlanCache{
 		Enabled:  false,
 		Capacity: 100,

diff --git a/config/config.toml.example b/config/config.toml.example
@@ -148,11 +148,6 @@ networks = ""
 # PROXY protocol header read timeout, unit is second
 header-timeout = 5
 
-[plan-cache]
-enabled = false
-capacity = 2560
-shards = 256
-
 [prepared-plan-cache]
 enabled = false
 capacity = 100

diff --git a/executor/aggregate_test.go b/executor/aggregate_test.go
@@ -17,7 +17,6 @@ import (
 	. "github.com/pingcap/check"
 	"github.com/pingcap/tidb/plan"
 	"github.com/pingcap/tidb/terror"
-	"github.com/pingcap/tidb/util/kvcache"
 	"github.com/pingcap/tidb/util/testkit"
 )
 
@@ -550,22 +549,6 @@ func (s *testSuite) TestAggEliminator(c *C) {
 	tk.MustQuery("select min(b*b) from t").Check(testkit.Rows("1"))
 }
 
-func (s *testSuite) TestIssue5663(c *C) {
-	tk := testkit.NewTestKitWithInit(c, s.store)
-	plan.GlobalPlanCache = kvcache.NewShardedLRUCache(2, 1)
-	planCahche := tk.Se.GetSessionVars().PlanCacheEnabled
-	defer func() {
-		tk.Se.GetSessionVars().PlanCacheEnabled = planCahche
-	}()
-
-	tk.Se.GetSessionVars().PlanCacheEnabled = true
-	tk.MustExec("drop table if exists t1;")
-	tk.MustExec("create table t1 (i int unsigned, primary key(i));")
-	tk.MustExec("insert into t1 values (1),(2),(3);")
-	tk.MustQuery("select group_concat(i) from t1 where i > 1;").Check(testkit.Rows("2,3"))
-	tk.MustQuery("select group_concat(i) from t1 where i > 1;").Check(testkit.Rows("2,3"))
-}
-
 func (s *testSuite) TestMaxMinFloatScalaFunc(c *C) {
 	tk := testkit.NewTestKitWithInit(c, s.store)
 

diff --git a/plan/cache.go b/plan/cache.go
@@ -16,7 +16,6 @@ package plan
 import (
 	"time"
 
-	"github.com/pingcap/tidb/ast"
 	"github.com/pingcap/tidb/mysql"
 	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/util/codec"
@@ -25,82 +24,12 @@ import (
 )
 
 var (
-	// GlobalPlanCache stores the global plan cache for every session in a tidb-server.
-	GlobalPlanCache *kvcache.ShardedLRUCache
-
 	// PreparedPlanCacheEnabled stores the global config "prepared-plan-cache-enabled".
 	PreparedPlanCacheEnabled bool
 	// PreparedPlanCacheCapacity stores the global config "prepared-plan-cache-capacity".
 	PreparedPlanCacheCapacity uint
 )
 
-type sqlCacheKey struct {
-	user           string
-	host           string
-	database       string
-	sql            string
-	snapshot       uint64
-	schemaVersion  int64
-	sqlMode        mysql.SQLMode
-	timezoneOffset int
-	readOnly       bool // stores the current tidb-server status.
-
-	hash []byte
-}
-
-// Hash implements Key interface.
-func (key *sqlCacheKey) Hash() []byte {
-	if key.hash == nil {
-		var (
-			userBytes  = hack.Slice(key.user)
-			hostBytes  = hack.Slice(key.host)
-			dbBytes    = hack.Slice(key.database)
-			sqlBytes   = hack.Slice(key.sql)
-			bufferSize = len(userBytes) + len(hostBytes) + len(dbBytes) + len(sqlBytes) + 8*4 + 1
-		)
-
-		key.hash = make([]byte, 0, bufferSize)
-		key.hash = append(key.hash, userBytes...)
-		key.hash = append(key.hash, hostBytes...)
-		key.hash = append(key.hash, dbBytes...)
-		key.hash = append(key.hash, sqlBytes...)
-		key.hash = codec.EncodeInt(key.hash, int64(key.snapshot))
-		key.hash = codec.EncodeInt(key.hash, key.schemaVersion)
-		key.hash = codec.EncodeInt(key.hash, int64(key.sqlMode))
-		key.hash = codec.EncodeInt(key.hash, int64(key.timezoneOffset))
-		if key.readOnly {
-			key.hash = append(key.hash, '1')
-		} else {
-			key.hash = append(key.hash, '0')
-		}
-	}
-	return key.hash
-}
-
-// NewSQLCacheKey creates a new sqlCacheKey object.
-func NewSQLCacheKey(sessionVars *variable.SessionVars, sql string, schemaVersion int64, readOnly bool) kvcache.Key {
-	timezoneOffset, user, host := 0, "", ""
-	if sessionVars.TimeZone != nil {
-		_, timezoneOffset = time.Now().In(sessionVars.TimeZone).Zone()
-	}
-	if sessionVars.User != nil {
-		user = sessionVars.User.Username
-		host = sessionVars.User.Hostname
-	}
-
-	return &sqlCacheKey{
-		user:           user,
-		host:           host,
-		database:       sessionVars.CurrentDB,
-		sql:            sql,
-		snapshot:       sessionVars.SnapshotTS,
-		schemaVersion:  schemaVersion,
-		sqlMode:        sessionVars.SQLMode,
-		timezoneOffset: timezoneOffset,
-		readOnly:       readOnly,
-	}
-}
-
 type pstmtPlanCacheKey struct {
 	database       string
 	connID         uint64
@@ -149,22 +78,6 @@ func NewPSTMTPlanCacheKey(sessionVars *variable.SessionVars, pstmtID uint32, sch
 	}
 }
 
-// SQLCacheValue stores the cached Statement and StmtNode.
-type SQLCacheValue struct {
-	StmtNode  ast.StmtNode
-	Plan      Plan
-	Expensive bool
-}
-
-// NewSQLCacheValue creates a SQLCacheValue.
-func NewSQLCacheValue(ast ast.StmtNode, plan Plan, expensive bool) *SQLCacheValue {
-	return &SQLCacheValue{
-		StmtNode:  ast,
-		Plan:      plan,
-		Expensive: expensive,
-	}
-}
-
 // PSTMTPlanCacheValue stores the cached Statement and StmtNode.
 type PSTMTPlanCacheValue struct {
 	Plan Plan

diff --git a/plan/cache_test.go b/plan/cache_test.go
@@ -38,8 +38,6 @@ func (s *testCacheSuite) SetUpSuite(c *C) {
 
 func (s *testCacheSuite) TestCacheKey(c *C) {
 	defer testleak.AfterTest(c)()
-	key1 := NewSQLCacheKey(s.ctx.GetSessionVars(), "select * from t", 0, false)
-	c.Assert(key1.Hash(), DeepEquals, []byte{0x74, 0x65, 0x73, 0x74, 0x73, 0x65, 0x6c, 0x65, 0x63, 0x74, 0x20, 0x2a, 0x20, 0x66, 0x72, 0x6f, 0x6d, 0x20, 0x74, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x30})
-	key2 := NewPSTMTPlanCacheKey(s.ctx.GetSessionVars(), 1, 1)
-	c.Assert(key2.Hash(), DeepEquals, []byte{0x74, 0x65, 0x73, 0x74, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0})
+	key := NewPSTMTPlanCacheKey(s.ctx.GetSessionVars(), 1, 1)
+	c.Assert(key.Hash(), DeepEquals, []byte{0x74, 0x65, 0x73, 0x74, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0})
 }
diff --git a/session/session.go b/session/session.go
@@ -767,86 +767,45 @@ func (s *session) execute(ctx context.Context, sql string) (recordSets []ast.Rec
 	}
 
 	s.PrepareTxnCtx(ctx)
-	var (
-		cacheKey         kvcache.Key
-		cacheValue       kvcache.Value
-		hitCache         = false
-		connID           = s.sessionVars.ConnectionID
-		planCacheEnabled = s.sessionVars.PlanCacheEnabled // Its value is read from the global configuration, and it will be only updated in tests.
-	)
+	connID := s.sessionVars.ConnectionID
+	err = s.loadCommonGlobalVariablesIfNeeded()
+	if err != nil {
+		return nil, errors.Trace(err)
+	}
 
-	if planCacheEnabled {
-		schemaVersion := domain.GetDomain(s).InfoSchema().SchemaMetaVersion()
-		readOnly := s.Txn() == nil || s.Txn().IsReadOnly()
+	charsetInfo, collation := s.sessionVars.GetCharsetInfo()
 
-		cacheKey = plan.NewSQLCacheKey(s.sessionVars, sql, schemaVersion, readOnly)
-		cacheValue, hitCache = plan.GlobalPlanCache.Get(cacheKey)
+	// Step1: Compile query string to abstract syntax trees(ASTs).
+	startTS := time.Now()
+	stmtNodes, err := s.ParseSQL(ctx, sql, charsetInfo, collation)
+	if err != nil {
+		s.rollbackOnError(ctx)
+		log.Warnf("con:%d parse error:\n%v\n%s", connID, err, sql)
+		return nil, errors.Trace(err)
 	}
+	metrics.SessionExecuteParseDuration.Observe(time.Since(startTS).Seconds())
 
-	if hitCache {
-		metrics.PlanCacheCounter.WithLabelValues("select").Inc()
-		stmtNode := cacheValue.(*plan.SQLCacheValue).StmtNode
-		stmt := &executor.ExecStmt{
-			InfoSchema: executor.GetInfoSchema(s),
-			Plan:       cacheValue.(*plan.SQLCacheValue).Plan,
-			Expensive:  cacheValue.(*plan.SQLCacheValue).Expensive,
-			Text:       stmtNode.Text(),
-			StmtNode:   stmtNode,
-			Ctx:        s,
-		}
-
+	compiler := executor.Compiler{Ctx: s}
+	for _, stmtNode := range stmtNodes {
 		s.PrepareTxnCtx(ctx)
-		if err = executor.ResetStmtCtx(s, stmtNode); err != nil {
-			return nil, errors.Trace(err)
-		}
-		if recordSets, err = s.executeStatement(ctx, connID, stmtNode, stmt, recordSets); err != nil {
-			return nil, errors.Trace(err)
-		}
-	} else {
-		err = s.loadCommonGlobalVariablesIfNeeded()
-		if err != nil {
+
+		// Step2: Transform abstract syntax tree to a physical plan(stored in executor.ExecStmt).
+		startTS = time.Now()
+		// Some executions are done in compile stage, so we reset them before compile.
+		if err := executor.ResetStmtCtx(s, stmtNode); err != nil {
 			return nil, errors.Trace(err)
 		}
-
-		charsetInfo, collation := s.sessionVars.GetCharsetInfo()
-
-		// Step1: Compile query string to abstract syntax trees(ASTs).
-		startTS := time.Now()
-		stmtNodes, err := s.ParseSQL(ctx, sql, charsetInfo, collation)
+		stmt, err := compiler.Compile(ctx, stmtNode)
 		if err != nil {
 			s.rollbackOnError(ctx)
-			log.Warnf("con:%d parse error:\n%v\n%s", connID, err, sql)
+			log.Warnf("con:%d compile error:\n%v\n%s", connID, err, sql)
 			return nil, errors.Trace(err)
 		}
-		metrics.SessionExecuteParseDuration.Observe(time.Since(startTS).Seconds())
-
-		compiler := executor.Compiler{Ctx: s}
-		for _, stmtNode := range stmtNodes {
-			s.PrepareTxnCtx(ctx)
+		metrics.SessionExecuteCompileDuration.Observe(time.Since(startTS).Seconds())
 
-			// Step2: Transform abstract syntax tree to a physical plan(stored in executor.ExecStmt).
-			startTS = time.Now()
-			// Some executions are done in compile stage, so we reset them before compile.
-			if err := executor.ResetStmtCtx(s, stmtNode); err != nil {
-				return nil, errors.Trace(err)
-			}
-			stmt, err := compiler.Compile(ctx, stmtNode)
-			if err != nil {
-				s.rollbackOnError(ctx)
-				log.Warnf("con:%d compile error:\n%v\n%s", connID, err, sql)
-				return nil, errors.Trace(err)
-			}
-			metrics.SessionExecuteCompileDuration.Observe(time.Since(startTS).Seconds())
-
-			// Step3: Cache the physical plan if possible.
-			if planCacheEnabled && stmt.Cacheable && len(stmtNodes) == 1 && !s.GetSessionVars().StmtCtx.HistogramsNotLoad() {
-				plan.GlobalPlanCache.Put(cacheKey, plan.NewSQLCacheValue(stmtNode, stmt.Plan, stmt.Expensive))
-			}
-
-			// Step4: Execute the physical plan.
-			if recordSets, err = s.executeStatement(ctx, connID, stmtNode, stmt, recordSets); err != nil {
-				return nil, errors.Trace(err)
-			}
+		// Step3: Execute the physical plan.
+		if recordSets, err = s.executeStatement(ctx, connID, stmtNode, stmt, recordSets); err != nil {
+			return nil, errors.Trace(err)
 		}
 	}
 

diff --git a/session/session_test.go b/session/session_test.go
@@ -27,7 +27,6 @@ import (
 	"github.com/pingcap/tidb/model"
 	"github.com/pingcap/tidb/mysql"
 	"github.com/pingcap/tidb/parser"
-	"github.com/pingcap/tidb/plan"
 	"github.com/pingcap/tidb/privilege/privileges"
 	"github.com/pingcap/tidb/session"
 	"github.com/pingcap/tidb/sessionctx"
@@ -38,7 +37,6 @@ import (
 	"github.com/pingcap/tidb/terror"
 	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/util/auth"
-	"github.com/pingcap/tidb/util/kvcache"
 	"github.com/pingcap/tidb/util/sqlexec"
 	"github.com/pingcap/tidb/util/testkit"
 	"github.com/pingcap/tidb/util/testleak"
@@ -110,18 +108,11 @@ func (p *mockBinlogPump) PullBinlogs(ctx context.Context, in *binlog.PullBinlogR
 }
 
 func (s *testSessionSuite) TestForCoverage(c *C) {
-	plan.GlobalPlanCache = kvcache.NewShardedLRUCache(2, 1)
-
 	// Just for test coverage.
 	tk := testkit.NewTestKitWithInit(c, s.store)
-	planCache := tk.Se.GetSessionVars().PlanCacheEnabled
-	defer func() {
-		tk.Se.GetSessionVars().PlanCacheEnabled = planCache
-	}()
 	tk.MustExec("drop table if exists t")
 	tk.MustExec("create table t (id int auto_increment, v int, index (id))")
 	tk.MustExec("insert t values ()")
-	tk.Se.GetSessionVars().PlanCacheEnabled = true
 	tk.MustExec("insert t values ()")
 	tk.MustExec("insert t values ()")
 

diff --git a/sessionctx/variable/session.go b/sessionctx/variable/session.go
@@ -206,9 +206,6 @@ type SessionVars struct {
 	// PlanID is the unique id of logical and physical plan.
 	PlanID int
 
-	// PlanCacheEnabled stores the global config "plan-cache-enabled", and it will be only updated in tests.
-	PlanCacheEnabled bool
-
 	// User is the user identity with which the session login.
 	User *auth.UserIdentity
 
@@ -341,7 +338,6 @@ func NewSessionVars() *SessionVars {
 	} else {
 		enableStreaming = "0"
 	}
-	vars.PlanCacheEnabled = config.GetGlobalConfig().PlanCache.Enabled
 	terror.Log(vars.SetSystemVar(TiDBEnableStreaming, enableStreaming))
 	return vars
 }

diff --git a/tidb-server/main.go b/tidb-server/main.go
@@ -44,7 +44,6 @@ import (
 	"github.com/pingcap/tidb/store/tikv/gcworker"
 	"github.com/pingcap/tidb/terror"
 	"github.com/pingcap/tidb/util"
-	"github.com/pingcap/tidb/util/kvcache"
 	"github.com/pingcap/tidb/util/logutil"
 	"github.com/pingcap/tidb/util/printer"
 	"github.com/pingcap/tidb/util/systimemon"
@@ -380,10 +379,6 @@ func setGlobalVars() {
 	plan.AllowCartesianProduct = cfg.Performance.CrossJoin
 	privileges.SkipWithGrant = cfg.Security.SkipGrantTable
 
-	if cfg.PlanCache.Enabled {
-		plan.GlobalPlanCache = kvcache.NewShardedLRUCache(cfg.PlanCache.Capacity, cfg.PlanCache.Shards)
-	}
-
 	plan.PreparedPlanCacheEnabled = cfg.PreparedPlanCache.Enabled
 	if plan.PreparedPlanCacheEnabled {
 		plan.PreparedPlanCacheCapacity = cfg.PreparedPlanCache.Capacity