feat: implement smart delete with shadow table support

DB.go

@@ -610,18 +610,30 @@ func (db *DB) Update(table string, data any, conditions string, args ...any) *Ex
 }
 
 func (db *DB) Delete(table string, conditions string, args ...any) *ExecResult {
-	if conditions != "" {
-		conditions = " where " + conditions
-	}
-	query := fmt.Sprintf("delete from %s%s", db.Quote(table), conditions)
-	r := baseExec(db.conn, nil, query, args...)
-	r.logger = db.logger
-	if r.Error != nil {
-		db.logger.LogQueryError(r.Error.Error(), query, args, r.usedTime)
-	} else {
-		if db.Config.LogSlow > 0 && r.usedTime >= float32(db.Config.LogSlow.TimeDuration()/time.Millisecond) {
-			db.logger.LogQuery(query, args, r.usedTime)
+	ts := db.getTable(table)
+	if !ts.HasShadowTable {
+		if conditions != "" {
+			conditions = " where " + conditions
 		}
+		query := fmt.Sprintf("delete from %s%s", db.Quote(table), conditions)
+		r := baseExec(db.conn, nil, query, args...)
+		r.logger = db.logger
+		if r.Error != nil {
+			db.logger.LogQueryError(r.Error.Error(), query, args, r.usedTime)
+		} else {
+			if db.Config.LogSlow > 0 && r.usedTime >= float32(db.Config.LogSlow.TimeDuration()/time.Millisecond) {
+				db.logger.LogQuery(query, args, r.usedTime)
+			}
+		}
+		return r
+	}
+
+	// Shadow delete
+	tx := db.Begin()
+	defer tx.CheckFinished()
+	r := tx.Delete(table, conditions, args...)
+	if r.Error == nil {
+		tx.Commit()
 	}
 	return r
 }

Tx.go

@@ -165,10 +165,23 @@ func (tx *Tx) Update(table string, data any, conditions string, args ...any) *Ex
 }
 
 func (tx *Tx) Delete(table string, conditions string, args ...any) *ExecResult {
+	ts := tx.db.getTable(table)
+	where := ""
 	if conditions != "" {
-		conditions = " where " + conditions
+		where = " where " + conditions
 	}
-	query := fmt.Sprintf("delete from %s%s", tx.Quote(table), conditions)
+
+	if ts.HasShadowTable {
+		// Move to shadow table
+		moveQuery := fmt.Sprintf("insert into %s select * from %s%s", tx.Quote(table+"_deleted"), tx.Quote(table), where)
+		r := baseExec(nil, tx.conn, moveQuery, args...)
+		if r.Error != nil {
+			tx.logger.LogQueryError(r.Error.Error(), moveQuery, args, r.usedTime)
+			return r
+		}
+	}
+
+	query := fmt.Sprintf("delete from %s%s", tx.Quote(table), where)
 	tx.lastSql = &query
 	tx.lastArgs = args
 	r := baseExec(nil, tx.conn, query, args...)

delete_test.go

@@ -0,0 +1,54 @@
+package db_test
+
+import (
+	"testing"
+	"apigo.cc/go/db"
+	_ "modernc.org/sqlite"
+)
+
+func TestSmartDelete(t *testing.T) {
+	dbInst := db.GetDB("sqlite://:memory:", nil)
+	
+	// Create table and shadow table
+	dbInst.Exec("CREATE TABLE orders (id INTEGER PRIMARY KEY, item TEXT)")
+	dbInst.Exec("CREATE TABLE orders_deleted (id INTEGER PRIMARY KEY, item TEXT)")
+
+	t.Run("ShadowDelete", func(t *testing.T) {
+		dbInst.Exec("INSERT INTO orders (id, item) VALUES (1, 'Phone')")
+		
+		res := dbInst.Delete("orders", "id = 1")
+		if res.Error != nil {
+			t.Fatalf("Delete failed: %v", res.Error)
+		}
+		if res.Changes() != 1 {
+			t.Errorf("Expected 1 change, got %d", res.Changes())
+		}
+
+		// Verify it's gone from main table
+		qr := dbInst.Query("SELECT COUNT(*) FROM orders WHERE id = 1")
+		count, _ := db.ToValue[int](qr)
+		if count != 0 {
+			t.Errorf("Expected 0 records in main table, got %d", count)
+		}
+
+		// Verify it's in shadow table
+		qr2 := dbInst.Query("SELECT COUNT(*) FROM orders_deleted WHERE id = 1")
+		countDeleted, _ := db.ToValue[int](qr2)
+		if countDeleted != 1 {
+			t.Errorf("Expected 1 record in shadow table, got %d", countDeleted)
+		}
+	})
+
+	t.Run("PhysicalDelete", func(t *testing.T) {
+		dbInst.Exec("CREATE TABLE logs (id INTEGER PRIMARY KEY, msg TEXT)")
+		dbInst.Exec("INSERT INTO logs (id, msg) VALUES (1, 'Login')")
+
+		dbInst.Delete("logs", "id = 1")
+		
+		qr := dbInst.Query("SELECT COUNT(*) FROM logs WHERE id = 1")
+		count, _ := db.ToValue[int](qr)
+		if count != 0 {
+			t.Errorf("Expected 0 records in logs, got %d", count)
+		}
+	})
+}