From 3b81313e1913df22bb7c6bad571cfa2b142b891e Mon Sep 17 00:00:00 2001
From: xgzlucario <912156837@qq.com>
Date: Wed, 31 Jul 2024 00:50:46 +0800
Subject: [PATCH] perf: optimize lookupCommand

---
 command.go | 33 ++++++++++++---------------------
 resp.go    |  3 +--
 rotom.go   | 28 ++++++++++++++--------------
 3 files changed, 27 insertions(+), 37 deletions(-)

diff --git a/command.go b/command.go
index 293d88e..16e58ee 100644
--- a/command.go
+++ b/command.go
@@ -1,7 +1,9 @@
 package main
 
 import (
+	"fmt"
 	"strconv"
+	"strings"
 
 	"github.com/xgzlucario/rotom/internal/dict"
 	"github.com/xgzlucario/rotom/internal/hash"
@@ -16,8 +18,8 @@ type Command struct {
 	// handler is this command real database handler function.
 	handler func(writer *RESPWriter, args []RESP)
 
-	// arity represents the minimal number of arguments that command accepts.
-	arity int
+	// minArgsNum represents the minimal number of arguments that command accepts.
+	minArgsNum int
 
 	// persist indicates whether this command needs to be persisted.
 	// effective when `appendonly` is true.
@@ -49,33 +51,22 @@ var cmdTable []*Command = []*Command{
 	{"mset", todoCommand, 0, false},
 	{"zpopmin", todoCommand, 0, false},
 	{"xadd", todoCommand, 0, false},
+	// TODO: distribution
+	{"sync", todoCommand, 0, false},
+	{"log", todoCommand, 0, false},
 }
 
-func lookupCommand(command string) *Command {
+func lookupCommand(name string) (*Command, error) {
 	for _, c := range cmdTable {
-		if equalCommand(command, c.name) {
-			return c
+		if len(name) == len(c.name) && strings.EqualFold(name, c.name) {
+			return c, nil
 		}
 	}
-	return nil
-}
-
-func equalCommand(str, lowerText string) bool {
-	if len(str) != len(lowerText) {
-		return false
-	}
-	const s = 'a' - 'A'
-	for i, lt := range lowerText {
-		delta := lt - rune(str[i])
-		if delta != 0 && delta != s {
-			return false
-		}
-	}
-	return true
+	return nil, fmt.Errorf("%w '%s'", errUnknownCommand, name)
 }
 
 func (cmd *Command) processCommand(writer *RESPWriter, args []RESP) {
-	if len(args) < cmd.arity {
+	if len(args) < cmd.minArgsNum {
 		writer.WriteError(errInvalidArguments)
 		return
 	}
diff --git a/resp.go b/resp.go
index caf826d..2ae4716 100644
--- a/resp.go
+++ b/resp.go
@@ -2,7 +2,6 @@ package main
 
 import (
 	"bytes"
-	"fmt"
 	"io"
 	"slices"
 	"strconv"
@@ -97,7 +96,7 @@ func (r *RESPReader) ReadNextCommand(argsBuf []RESP) (args []RESP, err error) {
 		// command_inline format
 		before, after, ok := cutByCRLF(r.b)
 		if !ok {
-			return nil, fmt.Errorf("%w '%s'", errUnknownCommand, r.b)
+			return nil, errInvalidArguments
 		}
 		args = append(args, before)
 		r.b = after
diff --git a/rotom.go b/rotom.go
index 8a66413..965eff6 100644
--- a/rotom.go
+++ b/rotom.go
@@ -1,7 +1,6 @@
 package main
 
 import (
-	"fmt"
 	"io"
 	"runtime"
 	"runtime/debug"
@@ -67,10 +66,10 @@ func InitDB(config *Config) (err error) {
 		// Load the initial data into memory by processing each stored command.
 		emptyWriter := NewWriter(WRITE_BUF_SIZE)
 		return db.aof.Read(func(args []RESP) {
-			command := args[0].ToString()
+			command := args[0].ToStringUnsafe()
 
-			cmd := lookupCommand(command)
-			if cmd != nil {
+			cmd, err := lookupCommand(command)
+			if err == nil {
 				cmd.processCommand(emptyWriter, args[1:])
 				emptyWriter.Reset()
 			}
@@ -154,23 +153,24 @@ func ProcessQueryBuf(client *Client) {
 		command := args[0].ToStringUnsafe()
 		args = args[1:]
 
-		cmd := lookupCommand(command)
-		if cmd != nil {
-			cmd.processCommand(client.replyWriter, args)
+		cmd, err := lookupCommand(command)
+		if err != nil {
+			client.replyWriter.WriteError(err)
+			log.Error().Msg(err.Error())
 
-			if server.outOfMemory {
+		} else {
+			// reject write request when OOM
+			if cmd.persist && server.outOfMemory {
 				client.replyWriter.WriteError(errOOM)
 				goto WRITE
 			}
 
-			if server.config.AppendOnly && cmd.persist {
+			cmd.processCommand(client.replyWriter, args)
+
+			// write aof file
+			if cmd.persist && server.config.AppendOnly {
 				db.aof.Write(queryBuf)
 			}
-
-		} else {
-			err := fmt.Errorf("%w '%s'", errUnknownCommand, command)
-			client.replyWriter.WriteError(err)
-			log.Error().Msg(err.Error())
 		}
 	}