expression: Optimize code if else branch logic

ddl/ddl.go

@@ -586,7 +586,8 @@ func (d *ddl) doDDLJob(ctx sessionctx.Context, job *model.Job) error {
 		if err != nil {
 			logutil.BgLogger().Error("[ddl] get history DDL job failed, check again", zap.Error(err))
 			continue
-		} else if historyJob == nil {
+		}
+		if historyJob == nil {
 			logutil.BgLogger().Debug("[ddl] DDL job is not in history, maybe not run", zap.Int64("jobID", jobID))
 			continue
 		}

distsql/distsql.go

@@ -37,8 +37,7 @@ func DispatchMPPTasks(ctx context.Context, sctx sessionctx.Context, tasks []*kv.
 	_, allowTiFlashFallback := sctx.GetSessionVars().AllowFallbackToTiKV[kv.TiFlash]
 	resp := sctx.GetMPPClient().DispatchMPPTasks(ctx, sctx.GetSessionVars().KVVars, tasks, allowTiFlashFallback)
 	if resp == nil {
-		err := errors.New("client returns nil response")
-		return nil, err
+		return nil, errors.New("client returns nil response")
 	}
 
 	encodeType := tipb.EncodeType_TypeDefault
@@ -91,8 +90,7 @@ func Select(ctx context.Context, sctx sessionctx.Context, kvReq *kv.Request, fie
 	}
 	resp := sctx.GetClient().Send(ctx, kvReq, sctx.GetSessionVars().KVVars, sctx.GetSessionVars().StmtCtx.MemTracker, enabledRateLimitAction, eventCb)
 	if resp == nil {
-		err := errors.New("client returns nil response")
-		return nil, err
+		return nil, errors.New("client returns nil response")
 	}
 
 	label := metrics.LblGeneral
@@ -139,13 +137,14 @@ func Select(ctx context.Context, sctx sessionctx.Context, kvReq *kv.Request, fie
 func SelectWithRuntimeStats(ctx context.Context, sctx sessionctx.Context, kvReq *kv.Request,
 	fieldTypes []*types.FieldType, fb *statistics.QueryFeedback, copPlanIDs []int, rootPlanID int) (SelectResult, error) {
 	sr, err := Select(ctx, sctx, kvReq, fieldTypes, fb)
-	if err == nil {
-		if selectResult, ok := sr.(*selectResult); ok {
-			selectResult.copPlanIDs = copPlanIDs
-			selectResult.rootPlanID = rootPlanID
-		}
+	if err != nil {
+		return nil, err
+	}
+	if selectResult, ok := sr.(*selectResult); ok {
+		selectResult.copPlanIDs = copPlanIDs
+		selectResult.rootPlanID = rootPlanID
 	}
-	return sr, err
+	return sr, nil
 }
 
 // Analyze do a analyze request.

server/conn.go

@@ -360,8 +360,7 @@ func (cc *clientConn) writeInitialHandshake(ctx context.Context) error {
 	data = append(data, 0)
 	// auth-plugin name
 	if cc.ctx == nil {
-		err := cc.openSession()
-		if err != nil {
+		if err := cc.openSession(); err != nil {
 			return err
 		}
 	}
@@ -374,15 +373,13 @@ func (cc *clientConn) writeInitialHandshake(ctx context.Context) error {
 
 	// Close the session to force this to be re-opened after we parse the response. This is needed
 	// to ensure we use the collation and client flags from the response for the session.
-	err = cc.ctx.Close()
-	if err != nil {
+	if err = cc.ctx.Close(); err != nil {
 		return err
 	}
 	cc.ctx = nil
 
 	data = append(data, 0)
-	err = cc.writePacket(data)
-	if err != nil {
+	if err = cc.writePacket(data); err != nil {
 		return err
 	}
 	return cc.flush(ctx)
@@ -1292,7 +1289,6 @@ func (cc *clientConn) dispatch(ctx context.Context, data []byte) error {
 	// ComProcessInfo, ComConnect, ComProcessKill, ComDebug
 	case mysql.ComPing:
 		return cc.writeOK(ctx)
-	// ComTime, ComDelayedInsert
 	case mysql.ComChangeUser:
 		return cc.handleChangeUser(ctx, data)
 	// ComBinlogDump, ComTableDump, ComConnectOut, ComRegisterSlave
@@ -1548,11 +1544,11 @@ func processStream(ctx context.Context, cc *clientConn, loadDataInfo *executor.L
 	}
 	if err != nil {
 		logutil.Logger(ctx).Error("load data process stream error", zap.Error(err))
-	} else {
-		err = loadDataInfo.EnqOneTask(ctx)
-		if err != nil {
-			logutil.Logger(ctx).Error("load data process stream error", zap.Error(err))
-		}
+		return
+	}
+	if err = loadDataInfo.EnqOneTask(ctx); err != nil {
+		logutil.Logger(ctx).Error("load data process stream error", zap.Error(err))
+		return
 	}
 }
 
@@ -1769,7 +1765,7 @@ func (cc *clientConn) handleQuery(ctx context.Context, sql string) (err error) {
 	var retryable bool
 	for i, stmt := range stmts {
 		if len(pointPlans) > 0 {
-			// Save the point plan in Session so we don't need to build the point plan again.
+			// Save the point plan in Session, so we don't need to build the point plan again.
 			cc.ctx.SetValue(plannercore.PointPlanKey, plannercore.PointPlanVal{Plan: pointPlans[i]})
 		}
 		retryable, err = cc.handleStmt(ctx, stmt, parserWarns, i == len(stmts)-1)
@@ -1897,7 +1893,7 @@ func (cc *clientConn) prefetchPointPlanKeys(ctx context.Context, stmts []ast.Stm
 }
 
 // The first return value indicates whether the call of handleStmt has no side effect and can be retried.
-// Currently the first return value is used to fallback to TiKV when TiFlash is down.
+// Currently, the first return value is used to fall back to TiKV when TiFlash is down.
 func (cc *clientConn) handleStmt(ctx context.Context, stmt ast.StmtNode, warns []stmtctx.SQLWarn, lastStmt bool) (bool, error) {
 	ctx = context.WithValue(ctx, execdetails.StmtExecDetailKey, &execdetails.StmtExecDetails{})
 	ctx = context.WithValue(ctx, util.ExecDetailsKey, &util.ExecDetails{})
@@ -1914,37 +1910,33 @@ func (cc *clientConn) handleStmt(ctx context.Context, stmt ast.StmtNode, warns [
 		return true, err
 	}
 
+	status := cc.ctx.Status()
 	if lastStmt {
 		cc.ctx.GetSessionVars().StmtCtx.AppendWarnings(warns)
-	}
-
-	status := cc.ctx.Status()
-	if !lastStmt {
+	} else {
 		status |= mysql.ServerMoreResultsExists
 	}
 
 	if rs != nil {
-		connStatus := atomic.LoadInt32(&cc.status)
-		if connStatus == connStatusShutdown {
+		if connStatus := atomic.LoadInt32(&cc.status); connStatus == connStatusShutdown {
 			return false, executor.ErrQueryInterrupted
 		}
-
-		retryable, err := cc.writeResultset(ctx, rs, false, status, 0)
-		if err != nil {
+		if retryable, err := cc.writeResultset(ctx, rs, false, status, 0); err != nil {
 			return retryable, err
 		}
-	} else {
-		handled, err := cc.handleQuerySpecial(ctx, status)
-		if handled {
-			execStmt := cc.ctx.Value(session.ExecStmtVarKey)
-			if execStmt != nil {
-				execStmt.(*executor.ExecStmt).FinishExecuteStmt(0, err, false)
-			}
-		}
-		if err != nil {
-			return false, err
+		return false, nil
+	}
+
+	handled, err := cc.handleQuerySpecial(ctx, status)
+	if handled {
+		if execStmt := cc.ctx.Value(session.ExecStmtVarKey); execStmt != nil {
+			execStmt.(*executor.ExecStmt).FinishExecuteStmt(0, err, false)
 		}
 	}
+	if err != nil {
+		return false, err
+	}
+
 	return false, nil
 }
 
@@ -2045,13 +2037,13 @@ func (cc *clientConn) writeResultset(ctx context.Context, rs ResultSet, binary b
 	}()
 	cc.initResultEncoder(ctx)
 	defer cc.rsEncoder.clean()
-	var err error
 	if mysql.HasCursorExistsFlag(serverStatus) {
-		err = cc.writeChunksWithFetchSize(ctx, rs, serverStatus, fetchSize)
-	} else {
-		retryable, err = cc.writeChunks(ctx, rs, binary, serverStatus)
+		if err := cc.writeChunksWithFetchSize(ctx, rs, serverStatus, fetchSize); err != nil {
+			return false, err
+		}
+		return false, cc.flush(ctx)
 	}
-	if err != nil {
+	if retryable, err := cc.writeChunks(ctx, rs, binary, serverStatus); err != nil {
 		return retryable, err
 	}
 
@@ -2109,8 +2101,7 @@ func (cc *clientConn) writeChunks(ctx context.Context, rs ResultSet, binary bool
 			// We need to call Next before we get columns.
 			// Otherwise, we will get incorrect columns info.
 			columns := rs.Columns()
-			err = cc.writeColumnInfo(columns, serverStatus)
-			if err != nil {
+			if err = cc.writeColumnInfo(columns, serverStatus); err != nil {
 				return false, err
 			}
 			gotColumnInfo = true
@@ -2151,13 +2142,11 @@ func (cc *clientConn) writeChunks(ctx context.Context, rs ResultSet, binary bool
 // fetchSize, the desired number of rows to be fetched each time when client uses cursor.
 func (cc *clientConn) writeChunksWithFetchSize(ctx context.Context, rs ResultSet, serverStatus uint16, fetchSize int) error {
 	fetchedRows := rs.GetFetchedRows()
-
-	req := rs.NewChunk(cc.chunkAlloc)
-	// if fetchedRows is not enough, getting data from recordSet.
 	for len(fetchedRows) < fetchSize {
+		// if fetchedRows is not enough, getting data from recordSet.
+		req := rs.NewChunk(cc.chunkAlloc)
 		// Here server.tidbResultSet implements Next method.
-		err := rs.Next(ctx, req)
-		if err != nil {
+		if err := rs.Next(ctx, req); err != nil {
 			return err
 		}
 		rowCount := req.NumRows()
@@ -2255,12 +2244,10 @@ func (cc *clientConn) handleChangeUser(ctx context.Context, data []byte) error {
 	dbName, _ := parseNullTermString(data)
 	cc.dbname = string(hack.String(dbName))
 
-	err := cc.ctx.Close()
-	if err != nil {
+	if err := cc.ctx.Close(); err != nil {
 		logutil.Logger(ctx).Debug("close old context failed", zap.Error(err))
 	}
-	err = cc.openSessionAndDoAuth(pass, "")
-	if err != nil {
+	if err := cc.openSessionAndDoAuth(pass, ""); err != nil {
 		return err
 	}
 	return cc.handleCommonConnectionReset(ctx)

server/server.go

@@ -225,7 +225,8 @@ func NewServer(cfg *config.Config, driver IDriver) (*Server, error) {
 	if tlsConfig != nil {
 		setSSLVariable(s.cfg.Security.SSLCA, s.cfg.Security.SSLKey, s.cfg.Security.SSLCert)
 		atomic.StorePointer(&s.tlsConfig, unsafe.Pointer(tlsConfig))
-		logutil.BgLogger().Info("mysql protocol server secure connection is enabled", zap.Bool("client verification enabled", len(variable.GetSysVar("ssl_ca").Value) > 0))
+		logutil.BgLogger().Info("mysql protocol server secure connection is enabled",
+			zap.Bool("client verification enabled", len(variable.GetSysVar("ssl_ca").Value) > 0))
 	} else if cfg.Security.RequireSecureTransport {
 		return nil, errSecureTransportRequired.FastGenByArgs()
 	}
@@ -250,9 +251,7 @@ func NewServer(cfg *config.Config, driver IDriver) (*Server, error) {
 	}
 
 	if s.cfg.Socket != "" {
-
-		err := cleanupStaleSocket(s.cfg.Socket)
-		if err != nil {
+		if err := cleanupStaleSocket(s.cfg.Socket); err != nil {
 			return nil, errors.Trace(err)
 		}
 
@@ -272,24 +271,23 @@ func NewServer(cfg *config.Config, driver IDriver) (*Server, error) {
 		if proxyTarget == nil {
 			proxyTarget = s.socket
 		}
-		pplistener, err := proxyprotocol.NewListener(proxyTarget, s.cfg.ProxyProtocol.Networks,
+		ppListener, err := proxyprotocol.NewListener(proxyTarget, s.cfg.ProxyProtocol.Networks,
 			int(s.cfg.ProxyProtocol.HeaderTimeout))
 		if err != nil {
 			logutil.BgLogger().Error("ProxyProtocol networks parameter invalid")
 			return nil, errors.Trace(err)
 		}
 		if s.listener != nil {
-			s.listener = pplistener
+			s.listener = ppListener
 			logutil.BgLogger().Info("server is running MySQL protocol (through PROXY protocol)", zap.String("host", s.cfg.Host))
 		} else {
-			s.socket = pplistener
+			s.socket = ppListener
 			logutil.BgLogger().Info("server is running MySQL protocol (through PROXY protocol)", zap.String("socket", s.cfg.Socket))
 		}
 	}
 
 	if s.cfg.Status.ReportStatus {
-		err = s.listenStatusHTTPServer()
-		if err != nil {
+		if err = s.listenStatusHTTPServer(); err != nil {
 			return nil, errors.Trace(err)
 		}
 	}
@@ -304,25 +302,26 @@ func NewServer(cfg *config.Config, driver IDriver) (*Server, error) {
 
 func cleanupStaleSocket(socket string) error {
 	sockStat, err := os.Stat(socket)
-	if err == nil {
-		if sockStat.Mode().Type() != os.ModeSocket {
-			return fmt.Errorf(
-				"the specified socket file %s is a %s instead of a socket file",
-				socket, sockStat.Mode().String())
-		}
+	if err != nil {
+		return nil
+	}
 
-		_, err = net.Dial("unix", socket)
-		if err != nil {
-			logutil.BgLogger().Warn("Unix socket exists and is nonfunctional, removing it",
-				zap.String("socket", socket), zap.Error(err))
-			err = os.Remove(socket)
-			if err != nil {
-				return fmt.Errorf("failed to remove socket file %s", socket)
-			}
-		} else {
-			return fmt.Errorf("unix socket %s exists and is functional, not removing it", socket)
-		}
+	if sockStat.Mode().Type() != os.ModeSocket {
+		return fmt.Errorf(
+			"the specified socket file %s is a %s instead of a socket file",
+			socket, sockStat.Mode().String())
+	}
+
+	if _, err = net.Dial("unix", socket); err == nil {
+		return fmt.Errorf("unix socket %s exists and is functional, not removing it", socket)
+	}
+
+	logutil.BgLogger().Warn("Unix socket exists and is nonfunctional, removing it",
+		zap.String("socket", socket), zap.Error(err))
+	if err = os.Remove(socket); err != nil {
+		return fmt.Errorf("failed to remove socket file %s", socket)
 	}
+
 	return nil
 }
 
@@ -363,7 +362,7 @@ func (s *Server) Run() error {
 		s.startStatusHTTP()
 	}
 	// If error should be reported and exit the server it can be sent on this
-	// channel. Otherwise end with sending a nil error to signal "done"
+	// channel. Otherwise, end with sending a nil error to signal "done"
 	errChan := make(chan error)
 	go s.startNetworkListener(s.listener, false, errChan)
 	go s.startNetworkListener(s.socket, true, errChan)
@@ -393,7 +392,7 @@ func (s *Server) startNetworkListener(listener net.Listener, isUnixSocket bool,
 				}
 			}
 
-			// If we got PROXY protocol error, we should continue accept.
+			// If we got PROXY protocol error, we should continue to accept.
 			if proxyprotocol.IsProxyProtocolError(err) {
 				logutil.BgLogger().Error("PROXY protocol failed", zap.Error(err))
 				continue
@@ -406,7 +405,6 @@ func (s *Server) startNetworkListener(listener net.Listener, isUnixSocket bool,
 
 		clientConn := s.newConn(conn)
 		if isUnixSocket {
-
 			uc, ok := conn.(*net.UnixConn)
 			if !ok {
 				logutil.BgLogger().Error("Expected UNIX socket, but got something else")
@@ -424,19 +422,20 @@ func (s *Server) startNetworkListener(listener net.Listener, isUnixSocket bool,
 
 		err = plugin.ForeachPlugin(plugin.Audit, func(p *plugin.Plugin) error {
 			authPlugin := plugin.DeclareAuditManifest(p.Manifest)
-			if authPlugin.OnConnectionEvent != nil {
-				host, _, err := clientConn.PeerHost("")
-				if err != nil {
-					logutil.BgLogger().Error("get peer host failed", zap.Error(err))
-					terror.Log(clientConn.Close())
-					return errors.Trace(err)
-				}
-				err = authPlugin.OnConnectionEvent(context.Background(), plugin.PreAuth, &variable.ConnectionInfo{Host: host})
-				if err != nil {
-					logutil.BgLogger().Info("do connection event failed", zap.Error(err))
-					terror.Log(clientConn.Close())
-					return errors.Trace(err)
-				}
+			if authPlugin.OnConnectionEvent == nil {
+				return nil
+			}
+			host, _, err := clientConn.PeerHost("")
+			if err != nil {
+				logutil.BgLogger().Error("get peer host failed", zap.Error(err))
+				terror.Log(clientConn.Close())
+				return errors.Trace(err)
+			}
+			if err = authPlugin.OnConnectionEvent(context.Background(), plugin.PreAuth,
+				&variable.ConnectionInfo{Host: host}); err != nil {
+				logutil.BgLogger().Info("do connection event failed", zap.Error(err))
+				terror.Log(clientConn.Close())
+				return errors.Trace(err)
 			}
 			return nil
 		})

session/session.go

@@ -1522,8 +1522,7 @@ func (s *session) ExecuteStmt(ctx context.Context, stmtNode ast.StmtNode) (sqlex
 	}
 
 	s.PrepareTxnCtx(ctx)
-	err := s.loadCommonGlobalVariablesIfNeeded()
-	if err != nil {
+	if err := s.loadCommonGlobalVariablesIfNeeded(); err != nil {
 		return nil, err
 	}