session, executor: support setting tidb_enable_stmt_summary in session scope (#12217)

domain/global_vars_cache.go

@@ -83,7 +83,7 @@ func checkEnableStmtSummary(rows []chunk.Row, fields []*ast.ResultField) {
 				}
 			}
 
-			stmtsummary.OnEnableStmtSummaryModified(sVal)
+			stmtsummary.StmtSummaryByDigestMap.SetEnabled(sVal, false)
 			break
 		}
 	}

domain/global_vars_cache_test.go

@@ -14,7 +14,6 @@
 package domain
 
 import (
-	"sync/atomic"
 	"time"
 
 	. "github.com/pingcap/check"
@@ -26,6 +25,7 @@ import (
 	"github.com/pingcap/tidb/store/mockstore"
 	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/util/chunk"
+	"github.com/pingcap/tidb/util/stmtsummary"
 	"github.com/pingcap/tidb/util/testleak"
 )
 
@@ -127,18 +127,18 @@ func (gvcSuite *testGVCSuite) TestCheckEnableStmtSummary(c *C) {
 		Collate: charset.CollationBin,
 	}
 
-	atomic.StoreInt32(&variable.EnableStmtSummary, 0)
+	stmtsummary.StmtSummaryByDigestMap.SetEnabled("0", false)
 	ck := chunk.NewChunkWithCapacity([]*types.FieldType{ft, ft1}, 1024)
 	ck.AppendString(0, variable.TiDBEnableStmtSummary)
 	ck.AppendString(1, "1")
 	row := ck.GetRow(0)
 	gvc.Update([]chunk.Row{row}, []*ast.ResultField{rf, rf1})
-	c.Assert(atomic.LoadInt32(&variable.EnableStmtSummary), Equals, int32(1))
+	c.Assert(stmtsummary.StmtSummaryByDigestMap.Enabled(), Equals, true)
 
 	ck = chunk.NewChunkWithCapacity([]*types.FieldType{ft, ft1}, 1024)
 	ck.AppendString(0, variable.TiDBEnableStmtSummary)
 	ck.AppendString(1, "0")
 	row = ck.GetRow(0)
 	gvc.Update([]chunk.Row{row}, []*ast.ResultField{rf, rf1})
-	c.Assert(atomic.LoadInt32(&variable.EnableStmtSummary), Equals, int32(0))
+	c.Assert(stmtsummary.StmtSummaryByDigestMap.Enabled(), Equals, false)
 }

executor/adapter.go

@@ -713,7 +713,7 @@ func (a *ExecStmt) LogSlowQuery(txnTS uint64, succ bool) {
 // SummaryStmt collects statements for performance_schema.events_statements_summary_by_digest
 func (a *ExecStmt) SummaryStmt() {
 	sessVars := a.Ctx.GetSessionVars()
-	if sessVars.InRestrictedSQL || atomic.LoadInt32(&variable.EnableStmtSummary) == 0 {
+	if sessVars.InRestrictedSQL || !stmtsummary.StmtSummaryByDigestMap.Enabled() {
 		return
 	}
 	stmtCtx := sessVars.StmtCtx

executor/set.go

@@ -30,6 +30,7 @@ import (
 	"github.com/pingcap/tidb/util/chunk"
 	"github.com/pingcap/tidb/util/gcutil"
 	"github.com/pingcap/tidb/util/logutil"
+	"github.com/pingcap/tidb/util/stmtsummary"
 	"go.uber.org/zap"
 )
 
@@ -119,6 +120,7 @@ func (e *SetExecutor) setSysVariable(name string, v *expression.VarAssignment) e
 	if sysVar.Scope == variable.ScopeNone {
 		return errors.Errorf("Variable '%s' is a read only variable", name)
 	}
+	var valStr string
 	if v.IsGlobal {
 		// Set global scope system variable.
 		if sysVar.Scope&variable.ScopeGlobal == 0 {
@@ -131,18 +133,18 @@ func (e *SetExecutor) setSysVariable(name string, v *expression.VarAssignment) e
 		if value.IsNull() {
 			value.SetString("")
 		}
-		svalue, err := value.ToString()
+		valStr, err = value.ToString()
 		if err != nil {
 			return err
 		}
-		err = sessionVars.GlobalVarsAccessor.SetGlobalSysVar(name, svalue)
+		err = sessionVars.GlobalVarsAccessor.SetGlobalSysVar(name, valStr)
 		if err != nil {
 			return err
 		}
 		err = plugin.ForeachPlugin(plugin.Audit, func(p *plugin.Plugin) error {
 			auditPlugin := plugin.DeclareAuditManifest(p.Manifest)
 			if auditPlugin.OnGlobalVariableEvent != nil {
-				auditPlugin.OnGlobalVariableEvent(context.Background(), e.ctx.GetSessionVars(), name, svalue)
+				auditPlugin.OnGlobalVariableEvent(context.Background(), e.ctx.GetSessionVars(), name, valStr)
 			}
 			return nil
 		})
@@ -179,7 +181,6 @@ func (e *SetExecutor) setSysVariable(name string, v *expression.VarAssignment) e
 			sessionVars.SnapshotTS = oldSnapshotTS
 			return err
 		}
-		var valStr string
 		if value.IsNull() {
 			valStr = "NULL"
 		} else {
@@ -190,6 +191,10 @@ func (e *SetExecutor) setSysVariable(name string, v *expression.VarAssignment) e
 		logutil.Logger(context.Background()).Info("set session var", zap.Uint64("conn", sessionVars.ConnectionID), zap.String("name", name), zap.String("val", valStr))
 	}
 
+	if name == variable.TiDBEnableStmtSummary {
+		stmtsummary.StmtSummaryByDigestMap.SetEnabled(valStr, !v.IsGlobal)
+	}
+
 	return nil
 }
 

infoschema/perfschema/tables_test.go

@@ -109,7 +109,7 @@ func (s *testTableSuite) TestStmtSummaryTable(c *C) {
 	).Check(testkit.Rows("test 4 4 insert into t values(1, 'a')"))
 
 	// Disable it again
-	tk.MustExec("set global tidb_enable_stmt_summary = 0")
+	tk.MustExec("set global tidb_enable_stmt_summary = false")
 	tk.MustQuery("select @@global.tidb_enable_stmt_summary").Check(testkit.Rows("0"))
 
 	// Create a new session to test
@@ -122,4 +122,36 @@ func (s *testTableSuite) TestStmtSummaryTable(c *C) {
 	tk.MustQuery(`select schema_name, exec_count, sum_rows_affected, query_sample_text 
 		from performance_schema.events_statements_summary_by_digest`,
 	).Check(testkit.Rows())
+
+	// Enable it in session scope
+	tk.MustExec("set session tidb_enable_stmt_summary = on")
+	// It should work immediately
+	tk.MustQuery("select * from t where a=2")
+	tk.MustQuery(`select schema_name, exec_count, sum_rows_affected, query_sample_text 
+		from performance_schema.events_statements_summary_by_digest
+		where digest_text like 'select * from t%'`,
+	).Check(testkit.Rows("test 1 0 select * from t where a=2"))
+
+	// Disable it in global scope
+	tk.MustExec("set global tidb_enable_stmt_summary = off")
+
+	// Create a new session to test
+	tk = testkit.NewTestKitWithInit(c, s.store)
+
+	tk.MustQuery("select * from t where a=2")
+
+	// Statement summary is still enabled
+	tk.MustQuery(`select schema_name, exec_count, sum_rows_affected, query_sample_text 
+		from performance_schema.events_statements_summary_by_digest
+		where digest_text like 'select * from t%'`,
+	).Check(testkit.Rows("test 2 0 select * from t where a=2"))
+
+	// Unset session variable
+	tk.MustExec("set session tidb_enable_stmt_summary = ''")
+	tk.MustQuery("select * from t where a=2")
+
+	// Statement summary is disabled
+	tk.MustQuery(`select schema_name, exec_count, sum_rows_affected, query_sample_text 
+		from performance_schema.events_statements_summary_by_digest`,
+	).Check(testkit.Rows())
 }

sessionctx/variable/sysvar.go

@@ -710,7 +710,7 @@ var defaultSysVars = []*SysVar{
 	{ScopeSession, TiDBLowResolutionTSO, "0"},
 	{ScopeSession, TiDBExpensiveQueryTimeThreshold, strconv.Itoa(DefTiDBExpensiveQueryTimeThreshold)},
 	{ScopeSession, TiDBAllowRemoveAutoInc, BoolToIntStr(DefTiDBAllowRemoveAutoInc)},
-	{ScopeGlobal, TiDBEnableStmtSummary, BoolToIntStr(DefTiDBEnableStmtSummary)},
+	{ScopeGlobal | ScopeSession, TiDBEnableStmtSummary, "0"},
 }
 
 // SynonymsSysVariables is synonyms of system variables.

sessionctx/variable/tidb_vars.go

@@ -351,7 +351,6 @@ const (
 	DefTiDBExpensiveQueryTimeThreshold = 60  // 60s
 	DefWaitSplitRegionTimeout          = 300 // 300s
 	DefTiDBAllowRemoveAutoInc          = false
-	DefTiDBEnableStmtSummary           = false
 )
 
 // Process global variables.
@@ -371,5 +370,4 @@ var (
 	MaxOfMaxAllowedPacket          uint64 = 1073741824
 	ExpensiveQueryTimeThreshold    uint64 = DefTiDBExpensiveQueryTimeThreshold
 	MinExpensiveQueryTimeThreshold uint64 = 10 //10s
-	EnableStmtSummary              int32  = BoolToInt32(DefTiDBEnableStmtSummary)
 )

sessionctx/variable/varsutil.go

@@ -420,7 +420,7 @@ func ValidateSetSystemVar(vars *SessionVars, name string, value string) (string,
 		TiDBOptInSubqToJoinAndAgg, TiDBEnableFastAnalyze,
 		TiDBBatchInsert, TiDBDisableTxnAutoRetry, TiDBEnableStreaming,
 		TiDBBatchDelete, TiDBBatchCommit, TiDBEnableCascadesPlanner, TiDBEnableWindowFunction,
-		TiDBCheckMb4ValueInUTF8, TiDBLowResolutionTSO, TiDBScatterRegion, TiDBEnableStmtSummary:
+		TiDBCheckMb4ValueInUTF8, TiDBLowResolutionTSO, TiDBScatterRegion:
 		if strings.EqualFold(value, "ON") || value == "1" || strings.EqualFold(value, "OFF") || value == "0" {
 			return value, nil
 		}
@@ -577,6 +577,16 @@ func ValidateSetSystemVar(vars *SessionVars, name string, value string) (string,
 			return "off", nil
 		}
 		return value, ErrWrongValueForVar.GenWithStackByArgs(name, value)
+	case TiDBEnableStmtSummary:
+		switch {
+		case strings.EqualFold(value, "ON") || value == "1":
+			return "1", nil
+		case strings.EqualFold(value, "OFF") || value == "0":
+			return "0", nil
+		case value == "":
+			return "", nil
+		}
+		return value, ErrWrongValueForVar.GenWithStackByArgs(name, value)
 	}
 	return value, nil
 }

util/stmtsummary/statement_summary.go

@@ -16,12 +16,10 @@ package stmtsummary
 import (
 	"strings"
 	"sync"
-	"sync/atomic"
 	"time"
 
 	"github.com/pingcap/parser/mysql"
 	"github.com/pingcap/tidb/config"
-	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/util/hack"
 	"github.com/pingcap/tidb/util/kvcache"
@@ -55,6 +53,15 @@ type stmtSummaryByDigestMap struct {
 	// It's rare to read concurrently, so RWMutex is not needed.
 	sync.Mutex
 	summaryMap *kvcache.SimpleLRUCache
+
+	// enabledWrapper encapsulates variables needed to judge whether statement summary is enabled.
+	enabledWrapper struct {
+		sync.RWMutex
+		// enabled indicates whether statement summary is enabled in current server.
+		sessionEnabled string
+		// setInSession indicates whether statement summary has been set in any session.
+		globalEnabled string
+	}
 }
 
 // StmtSummaryByDigestMap is a global map containing all statement summaries.
@@ -97,9 +104,13 @@ type StmtExecInfo struct {
 // newStmtSummaryByDigestMap creates an empty stmtSummaryByDigestMap.
 func newStmtSummaryByDigestMap() *stmtSummaryByDigestMap {
 	maxStmtCount := config.GetGlobalConfig().StmtSummary.MaxStmtCount
-	return &stmtSummaryByDigestMap{
+	ssMap := &stmtSummaryByDigestMap{
 		summaryMap: kvcache.NewSimpleLRUCache(maxStmtCount, 0, 0),
 	}
+	// enabledWrapper.defaultEnabled will be initialized in package variable.
+	ssMap.enabledWrapper.sessionEnabled = ""
+	ssMap.enabledWrapper.globalEnabled = ""
+	return ssMap
 }
 
 // newStmtSummaryByDigest creates a stmtSummaryByDigest from StmtExecInfo
@@ -164,7 +175,7 @@ func (ssMap *stmtSummaryByDigestMap) AddStatement(sei *StmtExecInfo) {
 
 	ssMap.Lock()
 	// Check again. Statements could be added before disabling the flag and after Clear()
-	if atomic.LoadInt32(&variable.EnableStmtSummary) == 0 {
+	if !ssMap.Enabled() {
 		ssMap.Unlock()
 		return
 	}
@@ -188,7 +199,7 @@ func (ssMap *stmtSummaryByDigestMap) Clear() {
 	ssMap.Unlock()
 }
 
-// Convert statement summary to Datum
+// ToDatum converts statement summary to Datum
 func (ssMap *stmtSummaryByDigestMap) ToDatum() [][]types.Datum {
 	ssMap.Lock()
 	values := ssMap.summaryMap.Values()
@@ -219,12 +230,64 @@ func (ssMap *stmtSummaryByDigestMap) ToDatum() [][]types.Datum {
 	return rows
 }
 
-// OnEnableStmtSummaryModified is triggered once EnableStmtSummary is modified.
-func OnEnableStmtSummaryModified(newValue string) {
-	if variable.TiDBOptOn(newValue) {
-		atomic.StoreInt32(&variable.EnableStmtSummary, 1)
+// SetEnabled enables or disables statement summary in global(cluster) or session(server) scope.
+func (ssMap *stmtSummaryByDigestMap) SetEnabled(value string, inSession bool) {
+	value = ssMap.normalizeEnableValue(value)
+
+	ssMap.enabledWrapper.Lock()
+	if inSession {
+		ssMap.enabledWrapper.sessionEnabled = value
+	} else {
+		ssMap.enabledWrapper.globalEnabled = value
+	}
+	sessionEnabled := ssMap.enabledWrapper.sessionEnabled
+	globalEnabled := ssMap.enabledWrapper.globalEnabled
+	ssMap.enabledWrapper.Unlock()
+
+	// Clear all summaries once statement summary is disabled.
+	var needClear bool
+	if ssMap.isSet(sessionEnabled) {
+		needClear = !ssMap.isEnabled(sessionEnabled)
+	} else {
+		needClear = !ssMap.isEnabled(globalEnabled)
+	}
+	if needClear {
+		ssMap.Clear()
+	}
+}
+
+// Enabled returns whether statement summary is enabled.
+func (ssMap *stmtSummaryByDigestMap) Enabled() bool {
+	ssMap.enabledWrapper.RLock()
+	var enabled bool
+	if ssMap.isSet(ssMap.enabledWrapper.sessionEnabled) {
+		enabled = ssMap.isEnabled(ssMap.enabledWrapper.sessionEnabled)
 	} else {
-		atomic.StoreInt32(&variable.EnableStmtSummary, 0)
-		StmtSummaryByDigestMap.Clear()
+		enabled = ssMap.isEnabled(ssMap.enabledWrapper.globalEnabled)
+	}
+	ssMap.enabledWrapper.RUnlock()
+	return enabled
+}
+
+// normalizeEnableValue converts 'ON' to '1' and 'OFF' to '0'
+func (ssMap *stmtSummaryByDigestMap) normalizeEnableValue(value string) string {
+	switch {
+	case strings.EqualFold(value, "ON"):
+		return "1"
+	case strings.EqualFold(value, "OFF"):
+		return "0"
+	default:
+		return value
 	}
 }
+
+// isEnabled converts a string value to bool.
+// 1 indicates true, 0 or '' indicates false.
+func (ssMap *stmtSummaryByDigestMap) isEnabled(value string) bool {
+	return value == "1"
+}
+
+// isSet judges whether the variable is set.
+func (ssMap *stmtSummaryByDigestMap) isSet(value string) bool {
+	return value != ""
+}