feat: 新增 DuckDB 方言支持及 SQLite3 自动注册 IF 函数

- 新增 dialect/duckdb 方言，支持 DuckDB SQL 语法
- 新增 schema/dialect/duckdb DDL 操作支持
- dialect/sqlite3: 注册 sqlite3_with_if 驱动，连接时自动注册 IF() 函数
- engine: MakeConnection 对 sqlite3 自动使用带 IF 支持的驱动
- engine: 新增 DBConfig DuckDB 配置项及相关 Option 函数
- 统一各方言测试引用路径

dialect/duckdb/duckdb.go

@@ -0,0 +1,38 @@
+package duckdb
+
+import (
+	_ "github.com/marcboeker/go-duckdb"
+
+	"git.fsdpf.net/go/db"
+)
+
+func DialectOptions() *db.SQLDialectOptions {
+	do := db.DefaultDialectOptions()
+
+	// DuckDB uses PostgreSQL-style placeholders ($1, $2, etc.)
+	do.PlaceHolderFragment = []byte("$")
+	do.IncludePlaceholderNum = true
+
+	// DuckDB supports most PostgreSQL features
+	do.SupportsReturn = true
+	do.SupportsOrderByOnUpdate = false
+	do.SupportsLimitOnUpdate = false
+	do.SupportsOrderByOnDelete = false
+	do.SupportsLimitOnDelete = false
+	do.SupportsConflictUpdateWhere = true
+	do.SupportsInsertIgnoreSyntax = false
+	do.SupportsConflictTarget = true
+	do.SupportsWithCTE = true
+	do.SupportsWithCTERecursive = true
+	do.SupportsDistinctOn = true
+	do.SupportsWindowFunction = true
+
+	// Use double quotes for identifiers (PostgreSQL-style)
+	do.QuoteRune = '"'
+
+	return do
+}
+
+func init() {
+	db.RegisterDialect("duckdb", DialectOptions())
+}

dialect/duckdb/duckdb_test.go

@@ -0,0 +1,135 @@
+package duckdb_test
+
+import (
+	"testing"
+
+	dbv2 "git.fsdpf.net/go/db"
+	"git.fsdpf.net/go/db/dialect/duckdb"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDialectOptions(t *testing.T) {
+	opts := duckdb.DialectOptions()
+	assert.NotNil(t, opts)
+	assert.Equal(t, '"', opts.QuoteRune)
+	assert.True(t, opts.IncludePlaceholderNum)
+	assert.Equal(t, []byte("$"), opts.PlaceHolderFragment)
+	assert.True(t, opts.SupportsReturn)
+	assert.True(t, opts.SupportsConflictTarget)
+	assert.True(t, opts.SupportsWithCTE)
+	assert.True(t, opts.SupportsDistinctOn)
+	assert.True(t, opts.SupportsWindowFunction)
+}
+
+func TestDialectRegistration(t *testing.T) {
+	// Verify the dialect is registered
+	dialect := dbv2.GetDialect("duckdb")
+	assert.NotNil(t, dialect)
+}
+
+func TestSelectSQL(t *testing.T) {
+	db := dbv2.Dialect("duckdb")
+
+	ds := db.From("users")
+	sql, _, err := ds.ToSQL()
+	assert.NoError(t, err)
+	assert.Equal(t, `SELECT * FROM "users"`, sql)
+
+	ds = db.From("users").Select("id", "name")
+	sql, _, err = ds.ToSQL()
+	assert.NoError(t, err)
+	assert.Equal(t, `SELECT "id", "name" FROM "users"`, sql)
+
+	ds = db.From("users").Where(dbv2.C("id").Eq(1))
+	sql, _, err = ds.ToSQL()
+	assert.NoError(t, err)
+	assert.Equal(t, `SELECT * FROM "users" WHERE ("id" = 1)`, sql)
+}
+
+func TestPreparedStatement(t *testing.T) {
+	db := dbv2.Dialect("duckdb")
+
+	ds := db.From("users").Prepared(true).Where(dbv2.C("id").Eq(1))
+	sql, args, err := ds.ToSQL()
+	assert.NoError(t, err)
+	assert.Equal(t, `SELECT * FROM "users" WHERE ("id" = $1)`, sql)
+	assert.Equal(t, []interface{}{int64(1)}, args)
+
+	ds = db.From("users").Prepared(true).Where(dbv2.C("name").Eq("John"))
+	sql, args, err = ds.ToSQL()
+	assert.NoError(t, err)
+	assert.Equal(t, `SELECT * FROM "users" WHERE ("name" = $1)`, sql)
+	assert.Equal(t, []interface{}{"John"}, args)
+}
+
+func TestInsertSQL(t *testing.T) {
+	db := dbv2.Dialect("duckdb")
+
+	ds := db.Insert("users").Rows(dbv2.Record{"id": 1, "name": "John"})
+	sql, _, err := ds.ToSQL()
+	assert.NoError(t, err)
+	assert.Contains(t, sql, `INSERT INTO "users"`)
+	assert.Contains(t, sql, `"id"`)
+	assert.Contains(t, sql, `"name"`)
+}
+
+func TestUpdateSQL(t *testing.T) {
+	db := dbv2.Dialect("duckdb")
+
+	ds := db.Update("users").Set(dbv2.Record{"name": "Jane"}).Where(dbv2.C("id").Eq(1))
+	sql, _, err := ds.ToSQL()
+	assert.NoError(t, err)
+	assert.Contains(t, sql, `UPDATE "users"`)
+	assert.Contains(t, sql, `"name"`)
+	assert.Contains(t, sql, `WHERE ("id" = 1)`)
+}
+
+func TestDeleteSQL(t *testing.T) {
+	db := dbv2.Dialect("duckdb")
+
+	ds := db.Delete("users").Where(dbv2.C("id").Eq(1))
+	sql, _, err := ds.ToSQL()
+	assert.NoError(t, err)
+	assert.Equal(t, `DELETE FROM "users" WHERE ("id" = 1)`, sql)
+}
+
+func TestJoinSQL(t *testing.T) {
+	db := dbv2.Dialect("duckdb")
+
+	ds := db.From("users").
+		Join(dbv2.T("orders"), dbv2.On(dbv2.Ex{"users.id": dbv2.I("orders.user_id")})).
+		Select("users.name", "orders.total")
+	sql, _, err := ds.ToSQL()
+	assert.NoError(t, err)
+	assert.Contains(t, sql, `FROM "users"`)
+	assert.Contains(t, sql, `INNER JOIN "orders"`)
+	assert.Contains(t, sql, `ON ("users"."id" = "orders"."user_id")`)
+}
+
+func TestWindowFunction(t *testing.T) {
+	db := dbv2.Dialect("duckdb")
+
+	ds := db.From("sales").
+		Select(
+			"product",
+			"amount",
+			dbv2.ROW_NUMBER().Over(dbv2.W().PartitionBy("product").OrderBy(dbv2.C("amount").Desc())).As("rank"),
+		)
+	sql, _, err := ds.ToSQL()
+	assert.NoError(t, err)
+	assert.Contains(t, sql, `ROW_NUMBER()`)
+	assert.Contains(t, sql, `OVER`)
+	assert.Contains(t, sql, `PARTITION BY`)
+}
+
+func TestCTE(t *testing.T) {
+	db := dbv2.Dialect("duckdb")
+
+	cte := db.From("users").Where(dbv2.C("active").IsTrue())
+	ds := db.From("active_users").With("active_users", cte).Select("*")
+	sql, _, err := ds.ToSQL()
+	assert.NoError(t, err)
+	assert.Contains(t, sql, `WITH active_users AS`)
+	assert.Contains(t, sql, `SELECT * FROM "users" WHERE ("active" IS TRUE)`)
+}

dialect/mysql/mysql.go

@@ -1,6 +1,8 @@
 package mysql
 
 import (
+	_ "github.com/go-sql-driver/mysql"
+
 	"git.fsdpf.net/go/db"
 	"git.fsdpf.net/go/db/exp"
 )

dialect/postgres/postgres.go

@@ -1,6 +1,10 @@
 package postgres
 
-import "git.fsdpf.net/go/db"
+import (
+	_ "github.com/lib/pq"
+
+	"git.fsdpf.net/go/db"
+)
 
 func DialectOptions() *db.SQLDialectOptions {
 	do := db.DefaultDialectOptions()

dialect/sqlite3/sqlite3.go

@@ -1,12 +1,18 @@
 package sqlite3
 
 import (
+	"database/sql"
 	"time"
 
 	"git.fsdpf.net/go/db"
 	"git.fsdpf.net/go/db/exp"
+	gosqlite3 "github.com/mattn/go-sqlite3"
 )
 
+// DriverWithIF 是注册了 IF() 函数的 SQLite3 驱动名称。
+// 使用该驱动名打开连接时，可在 SQL 中直接使用 IF(condition, trueVal, falseVal)。
+const DriverWithIF = "sqlite3_with_if"
+
 func DialectOptions() *db.SQLDialectOptions {
 	opts := db.DefaultDialectOptions()
 
@@ -72,5 +78,15 @@ func DialectOptions() *db.SQLDialectOptions {
 }
 
 func init() {
+	sql.Register(DriverWithIF, &gosqlite3.SQLiteDriver{
+		ConnectHook: func(conn *gosqlite3.SQLiteConn) error {
+			return conn.RegisterFunc("IF", func(cond int64, trueVal, falseVal interface{}) interface{} {
+				if cond != 0 {
+					return trueVal
+				}
+				return falseVal
+			}, true)
+		},
+	})
 	db.RegisterDialect("sqlite3", DialectOptions())
 }

dialect/sqlserver/sqlserver.go

@@ -1,6 +1,8 @@
 package sqlserver
 
 import (
+	_ "github.com/microsoft/go-mssqldb" // SQL Server driver
+
 	"git.fsdpf.net/go/db"
 	"git.fsdpf.net/go/db/exp"
 	"git.fsdpf.net/go/db/sqlgen"

dialect/sqlserver/sqlserver_test.go

@@ -11,7 +11,7 @@ import (
 
 	dbv2 "git.fsdpf.net/go/db"
 	_ "git.fsdpf.net/go/db/dialect/sqlserver"
-	_ "github.com/denisenkom/go-mssqldb"
+	_ "github.com/microsoft/go-mssqldb"
 	"github.com/stretchr/testify/suite"
 )