feat: add schema dump command for AI database discovery

README.md

@@ -101,6 +101,7 @@ xsql query "<SQL>" -p <profile> -f json
 
 ## 可用命令
 - xsql query "SQL" -p <profile> -f json  # 执行查询
+- xsql schema dump -p <profile> -f json  # 导出数据库结构
 - xsql profile list -f json               # 列出所有 profile
 - xsql profile show <name> -f json        # 查看 profile 详情
 
@@ -146,6 +147,7 @@ xsql query "<SQL>" -p <profile> -f json
 
 使用 xsql 工具查询数据库：
 - 查询: `xsql query "SELECT ..." -p <profile> -f json`
+- 导出结构: `xsql schema dump -p <profile> -f json`
 - 列出配置: `xsql profile list -f json`
 
 注意: 默认只读模式，写操作需要 --unsafe-allow-write 标志。
@@ -160,6 +162,7 @@ xsql query "<SQL>" -p <profile> -f json
 | 命令 | 说明 |
 |------|------|
 | `xsql query <SQL>` | 执行 SQL 查询（默认只读） |
+| `xsql schema dump` | 导出数据库结构（表、列、索引、外键） |
 | `xsql profile list` | 列出所有 profile |
 | `xsql profile show <name>` | 查看 profile 详情（密码脱敏） |
 | `xsql mcp server` | 启动 MCP Server（AI 助手集成） |
@@ -182,6 +185,33 @@ id  name
 (1 rows)
 ```
 
+### Schema 发现（AI 自动理解数据库）
+
+```bash
+# 导出数据库结构（供 AI 理解表结构）
+xsql schema dump -p dev -f json
+
+# 过滤特定表
+xsql schema dump -p dev --table "user*" -f json
+
+# 输出示例
+{
+  "ok": true,
+  "data": {
+    "database": "mydb",
+    "tables": [
+      {
+        "name": "users",
+        "columns": [
+          {"name": "id", "type": "bigint", "primary_key": true},
+          {"name": "email", "type": "varchar(255)", "nullable": false}
+        ]
+      }
+    ]
+  }
+}
+```
+
 ### SSH 隧道连接
 
 ```yaml

cmd/xsql/command_unit_test.go

@@ -3,19 +3,13 @@ package main
 import (
 	"bytes"
 	"context"
-	"database/sql"
-	"database/sql/driver"
 	"encoding/json"
-	"fmt"
-	"io"
 	"os"
 	"path/filepath"
 	"testing"
-	"time"
 
 	"github.com/zx06/xsql/internal/app"
 	"github.com/zx06/xsql/internal/config"
-	xdb "github.com/zx06/xsql/internal/db"
 	"github.com/zx06/xsql/internal/errors"
 	"github.com/zx06/xsql/internal/output"
 )
@@ -98,27 +92,116 @@ func TestRunQuery_MissingDB(t *testing.T) {
 	}
 }
 
-func TestRunQuery_Success(t *testing.T) {
-	driverName := registerStubDriver(t, map[string]*stubRows{
-		"select 1": {
-			columns: []string{"value"},
-			rows:    [][]driver.Value{{1}},
-		},
-	})
+func TestRunQuery_UnsupportedDriver(t *testing.T) {
+	GlobalConfig.Resolved.Profile = configProfile("sqlite")
+	GlobalConfig.FormatStr = "json"
 
+	var out bytes.Buffer
+	w := output.New(&out, &bytes.Buffer{})
+	err := runQuery(nil, []string{"select 1"}, &QueryFlags{}, &w)
+	if err == nil {
+		t.Fatal("expected error for unsupported driver")
+	}
+	if xe, ok := errors.As(err); !ok || xe.Code != errors.CodeDBDriverUnsupported {
+		t.Fatalf("expected CodeDBDriverUnsupported, got %v", err)
+	}
+}
+
+func TestRunQuery_PlaintextPasswordNotAllowed(t *testing.T) {
 	GlobalConfig.Resolved.Profile = config.Profile{
-		DB: driverName,
+		DB:             "mysql",
+		Password:       "plain_password",
+		AllowPlaintext: false,
 	}
 	GlobalConfig.FormatStr = "json"
 
 	var out bytes.Buffer
 	w := output.New(&out, &bytes.Buffer{})
-	err := runQuery(nil, []string{"select 1"}, &QueryFlags{UnsafeAllowWrite: true}, &w)
-	if err != nil {
-		t.Fatalf("unexpected error: %v", err)
+	err := runQuery(nil, []string{"select 1"}, &QueryFlags{}, &w)
+	if err == nil {
+		t.Fatal("expected error for plaintext password not allowed")
 	}
-	if !json.Valid(out.Bytes()) {
-		t.Fatalf("expected json output, got %s", out.String())
+	if xe, ok := errors.As(err); !ok || xe.Code != errors.CodeCfgInvalid {
+		t.Fatalf("expected CodeCfgInvalid, got %v", err)
+	}
+}
+
+func TestRunSchemaDump_UnsupportedDriver(t *testing.T) {
+	GlobalConfig.Resolved.Profile = configProfile("sqlite")
+	GlobalConfig.FormatStr = "json"
+
+	var out bytes.Buffer
+	w := output.New(&out, &bytes.Buffer{})
+	err := runSchemaDump(nil, nil, &SchemaFlags{}, &w)
+	if err == nil {
+		t.Fatal("expected error for unsupported driver")
+	}
+	if xe, ok := errors.As(err); !ok || xe.Code != errors.CodeDBDriverUnsupported {
+		t.Fatalf("expected CodeDBDriverUnsupported, got %v", err)
+	}
+}
+
+func TestRunSchemaDump_PlaintextPasswordNotAllowed(t *testing.T) {
+	GlobalConfig.Resolved.Profile = config.Profile{
+		DB:             "mysql",
+		Password:       "plain_password",
+		AllowPlaintext: false,
+	}
+	GlobalConfig.FormatStr = "json"
+
+	var out bytes.Buffer
+	w := output.New(&out, &bytes.Buffer{})
+	err := runSchemaDump(nil, nil, &SchemaFlags{}, &w)
+	if err == nil {
+		t.Fatal("expected error for plaintext password not allowed")
+	}
+	if xe, ok := errors.As(err); !ok || xe.Code != errors.CodeCfgInvalid {
+		t.Fatalf("expected CodeCfgInvalid, got %v", err)
+	}
+}
+
+func TestRunQuery_InvalidFormat(t *testing.T) {
+	GlobalConfig.Resolved.Profile = configProfile("mysql")
+	GlobalConfig.FormatStr = "invalid"
+
+	var out bytes.Buffer
+	w := output.New(&out, &bytes.Buffer{})
+	err := runQuery(nil, []string{"select 1"}, &QueryFlags{}, &w)
+	if err == nil {
+		t.Fatal("expected error for invalid format")
+	}
+	if xe, ok := errors.As(err); !ok || xe.Code != errors.CodeCfgInvalid {
+		t.Fatalf("expected CodeCfgInvalid, got %v", err)
+	}
+}
+
+func TestRunSchemaDump_MissingDB(t *testing.T) {
+	GlobalConfig.Resolved.Profile = configProfile("")
+	GlobalConfig.FormatStr = "json"
+
+	var out bytes.Buffer
+	w := output.New(&out, &bytes.Buffer{})
+	err := runSchemaDump(nil, nil, &SchemaFlags{}, &w)
+	if err == nil {
+		t.Fatal("expected error for missing db type")
+	}
+	if xe, ok := errors.As(err); !ok || xe.Code != errors.CodeCfgInvalid {
+		t.Fatalf("expected CodeCfgInvalid, got %v", err)
+	}
+}
+
+func TestRunSchemaDump_InvalidFormat(t *testing.T) {
+	GlobalConfig.Resolved.Profile = configProfile("mysql")
+	GlobalConfig.FormatStr = "invalid"
+
+	var out bytes.Buffer
+	w := output.New(&out, &bytes.Buffer{})
+	err := runSchemaDump(nil, nil, &SchemaFlags{}, &w)
+	if err == nil {
+		t.Fatal("expected error for invalid format")
+	}
+	if xe, ok := errors.As(err); !ok || xe.Code != errors.CodeCfgInvalid {
+		t.Fatalf("expected CodeCfgInvalid, got %v", err)
 	}
 }
 
@@ -516,104 +599,24 @@ profiles:
 	}
 }
 
-func configProfile(dbType string) config.Profile {
-	return config.Profile{DB: dbType}
-}
-
-type stubDriver struct {
-	responseRows map[string]*stubRows
-}
-
-type stubConnector struct {
-	driver *stubDriver
-}
-
-func (c *stubConnector) Connect(context.Context) (driver.Conn, error) {
-	return &stubConn{driver: c.driver}, nil
-}
-
-func (c *stubConnector) Driver() driver.Driver {
-	return c.driver
-}
-
-func (d *stubDriver) Open(string) (driver.Conn, error) {
-	return &stubConn{driver: d}, nil
-}
-
-type stubConn struct {
-	driver *stubDriver
-}
-
-func (c *stubConn) Prepare(string) (driver.Stmt, error) {
-	return nil, fmt.Errorf("prepare not supported")
-}
-
-func (c *stubConn) Close() error {
-	return nil
-}
-
-func (c *stubConn) Begin() (driver.Tx, error) {
-	return &stubTx{}, nil
-}
-
-func (c *stubConn) QueryContext(ctx context.Context, query string, args []driver.NamedValue) (driver.Rows, error) {
-	if rows, ok := c.driver.responseRows[query]; ok {
-		return rows, nil
+func TestValueIfSet(t *testing.T) {
+	if got := valueIfSet(false, "x"); got != "" {
+		t.Fatalf("expected empty when not set, got %q", got)
 	}
-	return nil, fmt.Errorf("unexpected query: %s", query)
-}
-
-type stubTx struct{}
-
-func (t *stubTx) Commit() error {
-	return nil
-}
-
-func (t *stubTx) Rollback() error {
-	return nil
-}
-
-type stubRows struct {
-	columns []string
-	rows    [][]driver.Value
-	idx     int
-}
-
-func (r *stubRows) Columns() []string {
-	return r.columns
-}
-
-func (r *stubRows) Close() error {
-	return nil
-}
-
-func (r *stubRows) Next(dest []driver.Value) error {
-	if r.idx >= len(r.rows) {
-		return io.EOF
+	if got := valueIfSet(true, "x"); got != "x" {
+		t.Fatalf("expected value when set, got %q", got)
 	}
-	copy(dest, r.rows[r.idx])
-	r.idx++
-	return nil
-}
-
-func registerStubDriver(t *testing.T, rows map[string]*stubRows) string {
-	t.Helper()
-
-	name := fmt.Sprintf("stub-%d", time.Now().UnixNano())
-	driver := &stubDriver{responseRows: rows}
-	db := sql.OpenDB(&stubConnector{driver: driver})
-	t.Cleanup(func() {
-		_ = db.Close()
-	})
-
-	xdb.Register(name, fakeDriver{db: db})
-	return name
 }
 
-type fakeDriver struct {
-	db *sql.DB
+func TestFirstNonEmpty(t *testing.T) {
+	if got := firstNonEmpty("", "", "a", "b"); got != "a" {
+		t.Fatalf("expected first non-empty value, got %q", got)
+	}
+	if got := firstNonEmpty("", ""); got != "" {
+		t.Fatalf("expected empty when all empty, got %q", got)
+	}
 }
 
-func (d fakeDriver) Open(ctx context.Context, opts xdb.ConnOptions) (*sql.DB, *errors.XError) {
-	return d.db, nil
+func configProfile(dbType string) config.Profile {
+	return config.Profile{DB: dbType}
 }

cmd/xsql/main.go

@@ -27,6 +27,7 @@ func run() int {
 	root.AddCommand(NewVersionCommand(&a, &w))
 	root.AddCommand(NewQueryCommand(&w))
 	root.AddCommand(NewProfileCommand(&w))
+	root.AddCommand(NewSchemaCommand(&w))
 	root.AddCommand(NewMCPCommand())
 	root.AddCommand(NewProxyCommand(&w))