🔧 fix(db/kingbase_impl): 修复标识符无条件加双引号导致SQL语法报错

- quoteKingbaseIdent 改为条件引用，仅对大写字母、保留字、特殊字符的标识符添加双引号
- 新增 kingbaseIdentNeedsQuote 判断标识符是否需要引用
- 新增 isKingbaseReservedWord 检测常见SQL保留字
- 补充 TestQuoteKingbaseIdent、TestKingbaseIdentNeedsQuote 单测覆盖各场景
- refs #176

internal/db/kingbase_impl.go

@@ -7,6 +7,7 @@ import (
 	"database/sql"
 	"fmt"
 	"net"
+	"regexp"
 	"strconv"
 	"strings"
 	"time"
@@ -805,12 +806,56 @@ func normalizeKingbaseIdentifier(raw string) string {
 	return value
 }
 
+// kingbaseIdentNeedsQuote 判断标识符是否需要双引号包裹。
+// 与前端 sql.ts 中 needsQuote 逻辑保持一致。
+func kingbaseIdentNeedsQuote(ident string) bool {
+	if ident == "" {
+		return false
+	}
+	// 不是合法裸标识符格式（必须以字母或下划线开头，仅含字母、数字、下划线）
+	if matched, _ := regexp.MatchString(`^[a-zA-Z_][a-zA-Z0-9_]*$`, ident); !matched {
+		return true
+	}
+	// 包含大写字母时需要引号保护（KingbaseES/PostgreSQL 默认将未加引号的标识符折叠为小写）
+	for _, r := range ident {
+		if r >= 'A' && r <= 'Z' {
+			return true
+		}
+	}
+	// 是 SQL 保留字
+	return isKingbaseReservedWord(ident)
+}
+
+// isKingbaseReservedWord 检查是否为常见 SQL 保留字（简化版，与前端保持一致）。
+func isKingbaseReservedWord(ident string) bool {
+	switch strings.ToLower(ident) {
+	case "select", "from", "where", "table", "index", "user", "order", "group", "by",
+		"limit", "offset", "and", "or", "not", "null", "true", "false", "key",
+		"primary", "foreign", "references", "default", "constraint",
+		"create", "drop", "alter", "insert", "update", "delete", "set", "values", "into",
+		"join", "left", "right", "inner", "outer", "on", "as", "is", "in", "like",
+		"between", "case", "when", "then", "else", "end", "having", "distinct",
+		"all", "any", "exists", "union", "except", "intersect",
+		"column", "check", "unique", "with", "grant", "revoke", "trigger",
+		"begin", "commit", "rollback", "schema", "database", "view", "function",
+		"procedure", "sequence", "type", "domain", "role", "session", "current",
+		"authorization", "cross", "full", "natural", "some", "cast", "fetch",
+		"for", "to", "do", "if", "return", "returns", "declare", "cursor":
+		return true
+	}
+	return false
+}
+
 func quoteKingbaseIdent(name string) string {
 	n := normalizeKingbaseIdentifier(name)
-	n = strings.ReplaceAll(n, `"`, `""`)
 	if n == "" {
 		return "\"\""
 	}
+	// 仅在需要时才加双引号，避免 KingbaseES 兼容性问题
+	if !kingbaseIdentNeedsQuote(n) {
+		return n
+	}
+	n = strings.ReplaceAll(n, `"`, `""`)
 	return `"` + n + `"`
 }
 

internal/db/kingbase_impl_test.go

@@ -34,10 +34,25 @@ func TestQuoteKingbaseIdent(t *testing.T) {
 		in   string
 		want string
 	}{
-		{name: "plain", in: "ldf_server", want: `"ldf_server"`},
-		{name: "double quoted", in: `""ldf_server""`, want: `"ldf_server"`},
-		{name: "escaped quoted", in: `\"ldf_server\"`, want: `"ldf_server"`},
+		// 纯小写+下划线：不加引号
+		{name: "plain lowercase", in: "ldf_server", want: "ldf_server"},
+		{name: "plain lowercase 2", in: "bcs_barcode", want: "bcs_barcode"},
+		{name: "double quoted input", in: `""ldf_server""`, want: "ldf_server"},
+		{name: "escaped quoted input", in: `\"ldf_server\"`, want: "ldf_server"},
+		// 含大写字母：加引号
+		{name: "uppercase", in: "LDF_Server", want: `"LDF_Server"`},
+		{name: "mixed case", in: "myTable", want: `"myTable"`},
+		// SQL 保留字：加引号
+		{name: "reserved word order", in: "order", want: `"order"`},
+		{name: "reserved word user", in: "user", want: `"user"`},
+		{name: "reserved word table", in: "table", want: `"table"`},
+		{name: "reserved word select", in: "select", want: `"select"`},
+		// 含特殊字符：加引号
+		{name: "with hyphen", in: "my-table", want: `"my-table"`},
+		{name: "with space", in: "my table", want: `"my table"`},
 		{name: "with embedded quote", in: `ab"cd`, want: `"ab""cd"`},
+		// 空值
+		{name: "empty", in: "", want: `""`},
 	}
 
 	for _, tt := range tests {
@@ -49,6 +64,31 @@ func TestQuoteKingbaseIdent(t *testing.T) {
 	}
 }
 
+func TestKingbaseIdentNeedsQuote(t *testing.T) {
+	tests := []struct {
+		name string
+		in   string
+		want bool
+	}{
+		{name: "plain lowercase", in: "ldf_server", want: false},
+		{name: "starts with underscore", in: "_col", want: false},
+		{name: "with digits", in: "col123", want: false},
+		{name: "uppercase", in: "MyTable", want: true},
+		{name: "reserved word", in: "order", want: true},
+		{name: "with hyphen", in: "my-col", want: true},
+		{name: "starts with digit", in: "123col", want: true},
+		{name: "empty", in: "", want: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := kingbaseIdentNeedsQuote(tt.in); got != tt.want {
+				t.Fatalf("kingbaseIdentNeedsQuote(%q) = %v, want %v", tt.in, got, tt.want)
+			}
+		})
+	}
+}
+
 func TestSplitKingbaseQualifiedTable(t *testing.T) {
 	tests := []struct {
 		name       string