Addition of @@enable_system_settings to vtgate

go/vt/sqlparser/ast_rewriting.go

@@ -235,6 +235,7 @@ func (er *expressionRewriter) sysVarRewrite(cursor *Cursor, node *ColName) {
 		sysvars.Workload.Name,
 		sysvars.DDLStrategy.Name,
 		sysvars.SessionUUID.Name,
+		sysvars.SessionEnableSystemSettings.Name,
 		sysvars.ReadAfterWriteGTID.Name,
 		sysvars.ReadAfterWriteTimeOut.Name,
 		sysvars.VitessVersion.Name,

go/vt/sqlparser/ast_rewriting_test.go

@@ -29,7 +29,7 @@ import (
 type myTestCase struct {
 	in, expected                                                      string
 	liid, db, foundRows, rowCount, rawGTID, rawTimeout, sessTrackGTID bool
-	ddlStrategy, sessionUUID                                          bool
+	ddlStrategy, sessionUUID, sessionEnableSystemSettings             bool
 	udv                                                               int
 	autocommit, clientFoundRows, skipQueryPlanCache                   bool
 	sqlSelectLimit, transactionMode, workload, vitessVersion          bool
@@ -44,6 +44,10 @@ func TestRewrites(in *testing.T) {
 		in:            "SELECT @@vitess_version",
 		expected:      "SELECT :__vtvitess_version as `@@vitess_version`",
 		vitessVersion: true,
+	}, {
+		in:                          "SELECT @@enable_system_settings",
+		expected:                    "SELECT :__vtenable_system_settings as `@@enable_system_settings`",
+		sessionEnableSystemSettings: true,
 	}, {
 		in:       "SELECT last_insert_id()",
 		expected: "SELECT :__lastInsertId as `last_insert_id()`",
@@ -199,6 +203,7 @@ func TestRewrites(in *testing.T) {
 			assert.Equal(tc.workload, result.NeedsSysVar(sysvars.Workload.Name), "should need :__vtworkload")
 			assert.Equal(tc.ddlStrategy, result.NeedsSysVar(sysvars.DDLStrategy.Name), "should need ddlStrategy")
 			assert.Equal(tc.sessionUUID, result.NeedsSysVar(sysvars.SessionUUID.Name), "should need sessionUUID")
+			assert.Equal(tc.sessionEnableSystemSettings, result.NeedsSysVar(sysvars.SessionEnableSystemSettings.Name), "should need sessionEnableSystemSettings")
 			assert.Equal(tc.rawGTID, result.NeedsSysVar(sysvars.ReadAfterWriteGTID.Name), "should need rawGTID")
 			assert.Equal(tc.rawTimeout, result.NeedsSysVar(sysvars.ReadAfterWriteTimeOut.Name), "should need rawTimeout")
 			assert.Equal(tc.sessTrackGTID, result.NeedsSysVar(sysvars.SessionTrackGTIDs.Name), "should need sessTrackGTID")

go/vt/sysvars/sysvars.go

@@ -43,17 +43,18 @@ var (
 	off  = "0"
 	utf8 = "'utf8'"
 
-	Autocommit          = SystemVariable{Name: "autocommit", IsBoolean: true, Default: on}
-	ClientFoundRows     = SystemVariable{Name: "client_found_rows", IsBoolean: true, Default: off}
-	SkipQueryPlanCache  = SystemVariable{Name: "skip_query_plan_cache", IsBoolean: true, Default: off}
-	TxReadOnly          = SystemVariable{Name: "tx_read_only", IsBoolean: true, Default: off}
-	TransactionReadOnly = SystemVariable{Name: "transaction_read_only", IsBoolean: true, Default: off}
-	SQLSelectLimit      = SystemVariable{Name: "sql_select_limit", Default: off}
-	TransactionMode     = SystemVariable{Name: "transaction_mode", IdentifierAsString: true}
-	Workload            = SystemVariable{Name: "workload", IdentifierAsString: true}
-	Charset             = SystemVariable{Name: "charset", Default: utf8, IdentifierAsString: true}
-	Names               = SystemVariable{Name: "names", Default: utf8, IdentifierAsString: true}
-	SessionUUID         = SystemVariable{Name: "session_uuid", IdentifierAsString: true}
+	Autocommit                  = SystemVariable{Name: "autocommit", IsBoolean: true, Default: on}
+	ClientFoundRows             = SystemVariable{Name: "client_found_rows", IsBoolean: true, Default: off}
+	SkipQueryPlanCache          = SystemVariable{Name: "skip_query_plan_cache", IsBoolean: true, Default: off}
+	TxReadOnly                  = SystemVariable{Name: "tx_read_only", IsBoolean: true, Default: off}
+	TransactionReadOnly         = SystemVariable{Name: "transaction_read_only", IsBoolean: true, Default: off}
+	SQLSelectLimit              = SystemVariable{Name: "sql_select_limit", Default: off}
+	TransactionMode             = SystemVariable{Name: "transaction_mode", IdentifierAsString: true}
+	Workload                    = SystemVariable{Name: "workload", IdentifierAsString: true}
+	Charset                     = SystemVariable{Name: "charset", Default: utf8, IdentifierAsString: true}
+	Names                       = SystemVariable{Name: "names", Default: utf8, IdentifierAsString: true}
+	SessionUUID                 = SystemVariable{Name: "session_uuid", IdentifierAsString: true}
+	SessionEnableSystemSettings = SystemVariable{Name: "enable_system_settings", IsBoolean: true, Default: on}
 	// Online DDL
 	DDLStrategy   = SystemVariable{Name: "ddl_strategy", IdentifierAsString: true}
 	VitessVersion = SystemVariable{Name: "vitess_version", IdentifierAsString: true}
@@ -76,6 +77,7 @@ var (
 		Charset,
 		Names,
 		SessionUUID,
+		SessionEnableSystemSettings,
 		ReadAfterWriteGTID,
 		ReadAfterWriteTimeOut,
 		SessionTrackGTIDs,

go/vt/vtgate/engine/fake_vcursor_test.go

@@ -73,6 +73,14 @@ func (t noopVCursor) SetReadAfterWriteGTID(s string) {
 	panic("implement me")
 }
 
+func (t noopVCursor) SetSessionEnableSystemSettings(allow bool) error {
+	panic("implement me")
+}
+
+func (t noopVCursor) GetSessionEnableSystemSettings() bool {
+	panic("implement me")
+}
+
 func (t noopVCursor) SetReadAfterWriteTimeout(f float64) {
 	panic("implement me")
 }

go/vt/vtgate/engine/primitive.go

@@ -134,6 +134,9 @@ type (
 
 		GetSessionUUID() string
 
+		SetSessionEnableSystemSettings(bool) error
+		GetSessionEnableSystemSettings() bool
+
 		// SetReadAfterWriteGTID sets the GTID that the user expects a replica to have caught up with before answering a query
 		SetReadAfterWriteGTID(string)
 		SetReadAfterWriteTimeout(float64)

go/vt/vtgate/engine/set.go

@@ -408,6 +408,8 @@ func (svss *SysVarSetAware) Execute(vcursor VCursor, env evalengine.ExpressionEn
 			return vterrors.Errorf(vtrpcpb.Code_INVALID_ARGUMENT, "invalid DDL strategy: %s", str)
 		}
 		vcursor.Session().SetDDLStrategy(str)
+	case sysvars.SessionEnableSystemSettings.Name:
+		err = svss.setBoolSysVar(env, vcursor.Session().SetSessionEnableSystemSettings)
 	case sysvars.Charset.Name, sysvars.Names.Name:
 		str, err := svss.evalAsString(env)
 		if err != nil {

go/vt/vtgate/executor.go

@@ -297,6 +297,8 @@ func (e *Executor) addNeededBindVars(bindVarNeeds *sqlparser.BindVarNeeds, bindV
 			bindVars[key] = sqltypes.StringBindVariable(session.DDLStrategy)
 		case sysvars.SessionUUID.Name:
 			bindVars[key] = sqltypes.StringBindVariable(session.SessionUUID)
+		case sysvars.SessionEnableSystemSettings.Name:
+			bindVars[key] = sqltypes.BoolBindVariable(session.EnableSystemSettings)
 		case sysvars.ReadAfterWriteGTID.Name:
 			var v string
 			ifReadAfterWriteExist(session, func(raw *vtgatepb.ReadAfterWrite) {

go/vt/vtgate/executor_set_test.go

@@ -228,6 +228,24 @@ func TestExecutorSet(t *testing.T) {
 	}, {
 		in:  "set session transaction read write",
 		out: &vtgatepb.Session{Autocommit: true},
+	}, {
+		in:  "set @@enable_system_settings = on",
+		out: &vtgatepb.Session{Autocommit: true, EnableSystemSettings: true},
+	}, {
+		in:  "set @@enable_system_settings = off",
+		out: &vtgatepb.Session{Autocommit: true, EnableSystemSettings: false},
+	}, {
+		in:  "set @@enable_system_settings = 1",
+		out: &vtgatepb.Session{Autocommit: true, EnableSystemSettings: true},
+	}, {
+		in:  "set @@enable_system_settings = 0",
+		out: &vtgatepb.Session{Autocommit: true, EnableSystemSettings: false},
+	}, {
+		in:  "set @@enable_system_settings = true",
+		out: &vtgatepb.Session{Autocommit: true, EnableSystemSettings: true},
+	}, {
+		in:  "set @@enable_system_settings = false",
+		out: &vtgatepb.Session{Autocommit: true, EnableSystemSettings: false},
 	}}
 	for i, tcase := range testcases {
 		t.Run(fmt.Sprintf("%d-%s", i, tcase.in), func(t *testing.T) {
@@ -247,76 +265,91 @@ func TestExecutorSetOp(t *testing.T) {
 	executor, _, _, sbclookup := createLegacyExecutorEnv()
 	*sysVarSetEnabled = true
 
-	sbclookup.SetResults([]*sqltypes.Result{
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("sql_mode", "varchar"), "STRICT_ALL_TABLES,NO_AUTO_UPDATES"),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("sql_safe_updates", "int64"), "1"),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("tx_isolation", "varchar"), "read-committed"),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("sql_quote_show_create", "int64"), "0"),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("foreign_key_checks", "int64")),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("unique_checks", "int64"), "0"),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("net_write_timeout", "int64"), "600"),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("net_read_timeout", "int64"), "300"),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("character_set_client", "varchar"), "utf8"),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("character_set_results", "varchar")),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("character_set_results", "varchar")),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("character_set_results", "varchar")),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("character_set_results", "varchar")),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("character_set_results", "varchar")),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("character_set_results", "varchar")),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("client_found_rows", "int64")),
-		sqltypes.MakeTestResult(sqltypes.MakeTestFields("client_found_rows", "int64")),
-	})
+	returnResult := func(columnName, typ, value string) *sqltypes.Result {
+		return sqltypes.MakeTestResult(sqltypes.MakeTestFields(columnName, typ), value)
+	}
+	returnNoResult := func(columnName, typ string) *sqltypes.Result {
+		return sqltypes.MakeTestResult(sqltypes.MakeTestFields(columnName, typ))
+	}
 
 	testcases := []struct {
-		in      string
-		warning []*querypb.QueryWarning
-		sysVars map[string]string
+		in              string
+		warning         []*querypb.QueryWarning
+		sysVars         map[string]string
+		disallowResConn bool
+		result          *sqltypes.Result
 	}{{
 		in: "set big_tables = 1", //ignore
 	}, {
 		in:      "set sql_mode = 'STRICT_ALL_TABLES,NO_AUTO_UPDATES'",
 		sysVars: map[string]string{"sql_mode": "'STRICT_ALL_TABLES,NO_AUTO_UPDATES'"},
+		result:  returnResult("sql_mode", "varchar", "STRICT_ALL_TABLES,NO_AUTO_UPDATES"),
+	}, {
+		// even though the tablet is saying that the value has changed,
+		// useReservedConn is false, so we won't allow this change
+		in:              "set sql_mode = 'STRICT_ALL_TABLES,NO_AUTO_UPDATES'",
+		result:          returnResult("sql_mode", "varchar", "STRICT_ALL_TABLES,NO_AUTO_UPDATES"),
+		sysVars:         nil,
+		disallowResConn: true,
 	}, {
 		in:      "set sql_safe_updates = 1",
 		sysVars: map[string]string{"sql_safe_updates": "1"},
+		result:  returnResult("sql_safe_updates", "int64", "1"),
 	}, {
 		in:      "set tx_isolation = 'read-committed'",
 		sysVars: map[string]string{"tx_isolation": "'read-committed'"},
+		result:  returnResult("tx_isolation", "varchar", "read-committed"),
 	}, {
 		in:      "set sql_quote_show_create = 0",
 		sysVars: map[string]string{"sql_quote_show_create": "0"},
+		result:  returnResult("sql_quote_show_create", "int64", "0"),
 	}, {
-		in: "set foreign_key_checks = 1",
+		in:     "set foreign_key_checks = 1",
+		result: returnNoResult("foreign_key_checks", "int64"),
 	}, {
 		in:      "set unique_checks = 0",
 		sysVars: map[string]string{"unique_checks": "0"},
+		result:  returnResult("unique_checks", "int64", "0"),
 	}, {
-		in: "set net_write_timeout = 600",
+		in:     "set net_write_timeout = 600",
+		result: returnResult("net_write_timeout", "int64", "600"),
 	}, {
-		in: "set net_read_timeout = 600",
+		in:     "set net_read_timeout = 600",
+		result: returnResult("net_read_timeout", "int64", "300"),
 	}, {
-		in: "set character_set_client = utf8",
+		in:     "set character_set_client = utf8",
+		result: returnResult("character_set_client", "varchar", "utf8"),
 	}, {
-		in: "set character_set_results=null",
+		in:     "set character_set_results=null",
+		result: returnNoResult("character_set_results", "varchar"),
 	}, {
-		in: "set character_set_results='binary'",
+		in:     "set character_set_results='binary'",
+		result: returnNoResult("character_set_results", "varchar"),
 	}, {
-		in: "set character_set_results='utf8'",
+		in:     "set character_set_results='utf8'",
+		result: returnNoResult("character_set_results", "varchar"),
 	}, {
-		in: "set character_set_results=utf8mb4",
+		in:     "set character_set_results=utf8mb4",
+		result: returnNoResult("character_set_results", "varchar"),
 	}, {
-		in: "set character_set_results='latin1'",
+		in:     "set character_set_results='latin1'",
+		result: returnNoResult("character_set_results", "varchar"),
 	}, {
-		in: "set character_set_results='abcd'",
+		in:     "set character_set_results='abcd'",
+		result: returnNoResult("character_set_results", "varchar"),
 	}, {
-		in: "set @@global.client_found_rows = 1",
+		in:     "set @@global.client_found_rows = 1",
+		result: returnNoResult("client_found_rows", "int64"),
 	}, {
-		in: "set global client_found_rows = 1",
+		in:     "set global client_found_rows = 1",
+		result: returnNoResult("client_found_rows", "int64"),
 	}}
 	for _, tcase := range testcases {
 		t.Run(tcase.in, func(t *testing.T) {
 			session := NewAutocommitSession(masterSession)
 			session.TargetString = KsTestUnsharded
+			session.EnableSystemSettings = !tcase.disallowResConn
+			sbclookup.SetResults([]*sqltypes.Result{tcase.result})
 			_, err := executor.Execute(
 				context.Background(),
 				"TestExecute",

go/vt/vtgate/plugin_mysql_server.go

@@ -342,9 +342,10 @@ func (vh *vtgateHandler) session(c *mysql.Conn) *vtgatepb.Session {
 				IncludedFields: querypb.ExecuteOptions_ALL,
 				Workload:       querypb.ExecuteOptions_Workload(mysqlDefaultWorkload),
 			},
-			Autocommit:  true,
-			DDLStrategy: *defaultDDLStrategy,
-			SessionUUID: u.String(),
+			Autocommit:           true,
+			DDLStrategy:          *defaultDDLStrategy,
+			SessionUUID:          u.String(),
+			EnableSystemSettings: *sysVarSetEnabled,
 		}
 		if c.Capabilities&mysql.CapabilityClientFoundRows != 0 {
 			session.Options.ClientFoundRows = true

go/vt/vtgate/safe_session.go

@@ -478,6 +478,20 @@ func (session *SafeSession) GetSessionUUID() string {
 	return session.SessionUUID
 }
 
+// SetSessionEnableSystemSettings set the SessionEnableSystemSettings setting.
+func (session *SafeSession) SetSessionEnableSystemSettings(allow bool) {
+	session.mu.Lock()
+	defer session.mu.Unlock()
+	session.EnableSystemSettings = allow
+}
+
+// GetSessionEnableSystemSettings returns the SessionEnableSystemSettings value.
+func (session *SafeSession) GetSessionEnableSystemSettings() bool {
+	session.mu.Lock()
+	defer session.mu.Unlock()
+	return session.EnableSystemSettings
+}
+
 // SetReadAfterWriteGTID set the ReadAfterWriteGtid setting.
 func (session *SafeSession) SetReadAfterWriteGTID(vtgtid string) {
 	session.mu.Lock()

go/vt/vtgate/vcursor_impl.go

@@ -329,7 +329,7 @@ func (vc *vcursorImpl) FirstSortedKeyspace() (*vindexes.Keyspace, error) {
 
 // SysVarSetEnabled implements the ContextVSchema interface
 func (vc *vcursorImpl) SysVarSetEnabled() bool {
-	return *sysVarSetEnabled
+	return vc.GetSessionEnableSystemSettings() && *sysVarSetEnabled
 }
 
 // KeyspaceExists provides whether the keyspace exists or not.
@@ -661,6 +661,17 @@ func (vc *vcursorImpl) GetSessionUUID() string {
 	return vc.safeSession.GetSessionUUID()
 }
 
+// SetSessionEnableSystemSettings implements the SessionActions interface
+func (vc *vcursorImpl) SetSessionEnableSystemSettings(allow bool) error {
+	vc.safeSession.SetSessionEnableSystemSettings(allow)
+	return nil
+}
+
+// GetSessionEnableSystemSettings implements the SessionActions interface
+func (vc *vcursorImpl) GetSessionEnableSystemSettings() bool {
+	return vc.safeSession.GetSessionEnableSystemSettings()
+}
+
 // SetReadAfterWriteGTID implements the SessionActions interface
 func (vc *vcursorImpl) SetReadAfterWriteGTID(vtgtid string) {
 	vc.safeSession.SetReadAfterWriteGTID(vtgtid)

proto/vtgate.proto

@@ -143,6 +143,9 @@ message Session {
 
   // Session UUID
   string SessionUUID = 22;
+
+  // enable_system_settings defines if we can use reserved connections.
+  bool enable_system_settings = 23;
 }
 
 // ReadAfterWrite contains information regarding gtid set and timeout