perf: pre-allocate all known length arrays to avoid re-scaling (#5029)

Co-authored-by: Kevin Wan <wanjunfeng@gmail.com>

core/conf/config.go

@@ -316,7 +316,7 @@ func toLowerCaseInterface(v any, info *fieldInfo) any {
 	case map[string]any:
 		return toLowerCaseKeyMap(vv, info)
 	case []any:
-		var arr []any
+		arr := make([]any, 0, len(vv))
 		for _, vvv := range vv {
 			arr = append(arr, toLowerCaseInterface(vvv, info))
 		}

core/discov/internal/registry.go

@@ -207,7 +207,7 @@ func (c *cluster) getCurrent(key watchKey) []KV {
 		return nil
 	}
 
-	var kvs []KV
+	kvs := make([]KV, 0, len(watcher.values))
 	for k, v := range watcher.values {
 		kvs = append(kvs, KV{
 			Key: k,
@@ -308,7 +308,7 @@ func (c *cluster) load(cli EtcdClient, key watchKey) int64 {
 		time.Sleep(coolDownUnstable.AroundDuration(coolDownInterval))
 	}
 
-	var kvs []KV
+	kvs := make([]KV, 0, len(resp.Kvs))
 	for _, ev := range resp.Kvs {
 		kvs = append(kvs, KV{
 			Key: string(ev.Key),
@@ -352,7 +352,7 @@ func (c *cluster) reload(cli EtcdClient) {
 	// cancel the previous watches
 	close(c.done)
 	c.watchGroup.Wait()
-	var keys []watchKey
+	keys := make([]watchKey, 0, len(c.watchers))
 	for wk, wval := range c.watchers {
 		keys = append(keys, wk)
 		if wval.cancel != nil {

core/logx/rotatelogger.go

@@ -211,7 +211,7 @@ func (r *SizeLimitRotateRule) OutdatedFiles() []string {
 		}
 	}
 
-	var result []string
+	result := make([]string, 0, len(outdated))
 	for k := range outdated {
 		result = append(result, k)
 	}

core/stores/redis/redis.go

@@ -1944,7 +1944,7 @@ func (s *Redis) ZaddsCtx(ctx context.Context, key string, ps ...Pair) (int64, er
 		return 0, err
 	}
 
-	var zs []red.Z
+	zs := make([]red.Z, 0, len(ps))
 	for _, p := range ps {
 		z := red.Z{Score: float64(p.Score), Member: p.Key}
 		zs = append(zs, z)

mcp/server.go

@@ -392,8 +392,8 @@ func (s *sseMcpServer) processListTools(ctx context.Context, client *mcpClient,
 		}
 	}
 
-	var toolsList []Tool
 	s.toolsLock.Lock()
+	toolsList := make([]Tool, 0, len(s.tools))
 	for _, tool := range s.tools {
 		if len(tool.InputSchema.Type) == 0 {
 			tool.InputSchema.Type = ContentTypeObject
@@ -437,8 +437,8 @@ func (s *sseMcpServer) processListPrompts(ctx context.Context, client *mcpClient
 	}
 
 	// Prepare prompt list
-	var promptsList []Prompt
 	s.promptsLock.Lock()
+	promptsList := make([]Prompt, 0, len(s.prompts))
 	for _, prompt := range s.prompts {
 		promptsList = append(promptsList, prompt)
 	}
@@ -475,8 +475,8 @@ func (s *sseMcpServer) processListResources(ctx context.Context, client *mcpClie
 		}
 	}
 
-	var resourcesList []Resource
 	s.resourcesLock.Lock()
+	resourcesList := make([]Resource, 0, len(s.resources))
 	for _, resource := range s.resources {
 		// Create a copy without the handler function which shouldn't be sent to clients
 		resourceCopy := Resource{

tools/goctl/api/dartgen/util.go

@@ -250,8 +250,9 @@ func extractPositionalParamsFromPath(route spec.Route) string {
 		return ""
 	}
 
-	var params []string
+	tagMembers := ds.GetTagMembers(pathTagKey)
-	for _, member := range ds.GetTagMembers(pathTagKey) {
+	params := make([]string, 0, len(tagMembers))
+	for _, member := range tagMembers {
 		dartType := member.Type.Name()
 		params = append(params, fmt.Sprintf("%s %s", dartType, getPropertyFromMember(member)))
 	}

tools/goctl/api/gogen/genconfig.go

@@ -36,13 +36,13 @@ func genConfig(dir string, cfg *config.Config, api *spec.ApiSpec) error {
 	}
 
 	authNames := getAuths(api)
-	var auths []string
+	auths := make([]string, 0, len(authNames))
 	for _, item := range authNames {
 		auths = append(auths, fmt.Sprintf("%s %s", item, jwtTemplate))
 	}
 
 	jwtTransNames := getJwtTrans(api)
-	var jwtTransList []string
+	jwtTransList := make([]string, 0, len(jwtTransNames))
 	for _, item := range jwtTransNames {
 		jwtTransList = append(jwtTransList, fmt.Sprintf("%s %s", item, jwtTransTemplate))
 	}

tools/goctl/api/gogen/genmain.go

@@ -43,7 +43,7 @@ func genMain(dir, rootPkg string, cfg *config.Config, api *spec.ApiSpec) error {
 }
 
 func genMainImports(parentPkg string) string {
-	var imports []string
+	imports := make([]string, 0, 5)
 	imports = append(imports, fmt.Sprintf("\"%s\"", pathx.JoinPackages(parentPkg, configDir)))
 	imports = append(imports, fmt.Sprintf("\"%s\"", pathx.JoinPackages(parentPkg, handlerDir)))
 	imports = append(imports, fmt.Sprintf("\"%s\"\n", pathx.JoinPackages(parentPkg, contextDir)))

tools/goctl/api/gogen/gentypes.go

@@ -154,7 +154,7 @@ func genTypesWithGroup(dir string, cfg *config.Config, api *spec.ApiSpec) error
 	}
 
 	for group, typeGroup := range groupTypes {
-		var types []spec.Type
+		types := make([]spec.Type, 0, len(typeGroup))
 		for _, v := range typeGroup {
 			types = append(types, v)
 		}

tools/goctl/api/parser/g4/ast/type.go

@@ -126,7 +126,7 @@ func (v *ApiVisitor) VisitTypeLit(ctx *api.TypeLitContext) any {
 // VisitTypeBlock implements from api.BaseApiParserVisitor
 func (v *ApiVisitor) VisitTypeBlock(ctx *api.TypeBlockContext) any {
 	list := ctx.AllTypeBlockBody()
-	var types []TypeExpr
+	types := make([]TypeExpr, 0, len(list))
 	for _, each := range list {
 		types = append(types, each.Accept(v).(TypeExpr))
 	}

tools/goctl/api/parser/parser.go

@@ -125,7 +125,7 @@ func (p parser) fillTypes() error {
 	for _, item := range p.ast.Type {
 		switch v := (item).(type) {
 		case *ast.TypeStruct:
-			var members []spec.Member
+			members := make([]spec.Member, 0, len(v.Fields))
 			for _, item := range v.Fields {
 				members = append(members, p.fieldToMember(item))
 			}

tools/goctl/api/spec/fn.go

@@ -20,11 +20,11 @@ const (
 var definedKeys = []string{bodyTagKey, formTagKey, pathTagKey, headerTagKey}
 
 func (s Service) JoinPrefix() Service {
-	var groups []Group
+	groups := make([]Group, 0, len(s.Groups))
 	for _, g := range s.Groups {
 		prefix := strings.TrimSpace(g.GetAnnotation(RoutePrefixKey))
 		prefix = strings.ReplaceAll(prefix, `"`, "")
-		var routes []Route
+		routes := make([]Route, 0, len(g.Routes))
 		for _, r := range g.Routes {
 			r.Path = path.Join("/", prefix, r.Path)
 			routes = append(routes, r)

tools/goctl/api/spec/tags.go

@@ -66,7 +66,7 @@ func (t *Tags) Keys() []string {
 	if t == nil {
 		return []string{}
 	}
-	var keys []string
+	keys := make([]string, 0, len(t.tags))
 	for _, tag := range t.tags {
 		keys = append(keys, tag.Key)
 	}

tools/goctl/api/swagger/api.go

@@ -19,7 +19,7 @@ func fillAllStructs(api *spec.ApiSpec) {
 	}
 
 	for _, group := range api.Service.Groups {
-		var routes []spec.Route
+		routes := make([]spec.Route, 0, len(group.Routes))
 		for _, route := range group.Routes {
 			route.RequestType = fillStruct("", route.RequestType, structTypes)
 			route.ResponseType = fillStruct("", route.ResponseType, structTypes)
@@ -74,7 +74,7 @@ func fillStruct(parent string, tp spec.Type, allTypes map[string]spec.DefineStru
 		val.Members = members
 		return val
 	case spec.NestedStruct:
-		var members []spec.Member
+		members := make([]spec.Member, 0, len(val.Members))
 		for _, member := range val.Members {
 			switch memberType := member.Type.(type) {
 			case spec.PointerType:

tools/goctl/api/swagger/options.go

@@ -67,11 +67,11 @@ func enumsValueFromOptions(options []string) []any {
 	}
 	for _, option := range options {
 		if strings.HasPrefix(option, enumFlag) {
-			var resp = make([]any, 0)
 			val := option[8:]
 			fields := util.FieldsAndTrimSpace(val, func(r rune) bool {
 				return r == '|'
 			})
+			var resp = make([]any, 0, len(fields))
 			for _, field := range fields {
 				resp = append(resp, field)
 			}

tools/goctl/api/swagger/swagger.go

@@ -244,7 +244,7 @@ func isOptional(_ Context, options []string) bool {
 
 func pathVariable2SwaggerVariable(_ Context, path string) string {
 	pathItems := strings.FieldsFunc(path, slashRune)
-	var resp []string
+	resp := make([]string, 0, len(pathItems))
 	for _, v := range pathItems {
 		if strings.HasPrefix(v, ":") {
 			resp = append(resp, "{"+v[1:]+"}")

tools/goctl/api/util/case.go

@@ -90,7 +90,7 @@ func ToUpperCase(r rune) rune {
 
 // ToLower returns a copy string by converting it into lower
 func ToLower(s string) string {
-	var out []rune
+	out := make([]rune, 0, len(s))
 	for _, r := range s {
 		out = append(out, ToLowerCase(r))
 	}
@@ -99,7 +99,7 @@ func ToLower(s string) string {
 
 // ToUpper returns a copy string by converting it into upper
 func ToUpper(s string) string {
-	var out []rune
+	out := make([]rune, 0, len(s))
 	for _, r := range s {
 		out = append(out, ToUpperCase(r))
 	}

tools/goctl/model/sql/command/command.go

@@ -172,7 +172,7 @@ func (p pattern) Match(s string) bool {
 }
 
 func (p pattern) list() []string {
-	var ret []string
+	ret := make([]string, 0, len(p))
 	for v := range p {
 		ret = append(ret, v)
 	}

tools/goctl/model/sql/gen/keys.go

@@ -39,7 +39,7 @@ type Join []string
 
 func genCacheKeys(prefix string, table parser.Table) (Key, []Key) {
 	var primaryKey Key
-	var uniqueKey []Key
+	uniqueKey := make([]Key, 0, len(table.UniqueIndex))
 	primaryKey = genCacheKey(prefix, table.Db, table.Name, []*parser.Field{&table.PrimaryKey.Field})
 	for _, each := range table.UniqueIndex {
 		uniqueKey = append(uniqueKey, genCacheKey(prefix, table.Db, table.Name, each))