From a8655f79477cc5d287a136d369141b5b9a468ba7 Mon Sep 17 00:00:00 2001
From: Jinzhu <wosmvp@gmail.com>
Date: Thu, 9 Jul 2020 12:15:35 +0800
Subject: [PATCH] Fix auto select with smaller struct for slices

---
 callbacks/query.go  | 24 +++++++++++++++++-------
 tests/query_test.go | 18 ++++++++++++++++++
 2 files changed, 35 insertions(+), 7 deletions(-)

diff --git a/callbacks/query.go b/callbacks/query.go
index 4b7f5bd5..9601f9bd 100644
--- a/callbacks/query.go
+++ b/callbacks/query.go
@@ -64,14 +64,24 @@ func BuildQuerySQL(db *gorm.DB) {
 				clauseSelect.Columns[idx] = clause.Column{Name: name, Raw: true}
 			}
 		}
-	} else if db.Statement.Schema != nil && db.Statement.ReflectValue.IsValid() && db.Statement.ReflectValue.Type() != db.Statement.Schema.ModelType {
-		stmt := gorm.Statement{DB: db}
-		// smaller struct
-		if err := stmt.Parse(db.Statement.Dest); err == nil {
-			clauseSelect.Columns = make([]clause.Column, len(stmt.Schema.DBNames))
+	} else if db.Statement.Schema != nil && db.Statement.ReflectValue.IsValid() {
+		smallerStruct := false
+		switch db.Statement.ReflectValue.Kind() {
+		case reflect.Struct:
+			smallerStruct = db.Statement.ReflectValue.Type() != db.Statement.Schema.ModelType
+		case reflect.Slice:
+			smallerStruct = db.Statement.ReflectValue.Type().Elem() != db.Statement.Schema.ModelType
+		}
 
-			for idx, dbName := range stmt.Schema.DBNames {
-				clauseSelect.Columns[idx] = clause.Column{Name: dbName}
+		if smallerStruct {
+			stmt := gorm.Statement{DB: db}
+			// smaller struct
+			if err := stmt.Parse(db.Statement.Dest); err == nil && stmt.Schema.ModelType != db.Statement.Schema.ModelType {
+				clauseSelect.Columns = make([]clause.Column, len(stmt.Schema.DBNames))
+
+				for idx, dbName := range stmt.Schema.DBNames {
+					clauseSelect.Columns[idx] = clause.Column{Name: dbName}
+				}
 			}
 		}
 	}
diff --git a/tests/query_test.go b/tests/query_test.go
index 1db490b7..62005e3a 100644
--- a/tests/query_test.go
+++ b/tests/query_test.go
@@ -177,6 +177,24 @@ func TestFillSmallerStruct(t *testing.T) {
 	if !regexp.MustCompile("SELECT .*id.*name.*updated_at.*created_at.* FROM .*users").MatchString(result.Statement.SQL.String()) {
 		t.Fatalf("SQL should include selected names, but got %v", result.Statement.SQL.String())
 	}
+
+	result = DB.Session(&gorm.Session{DryRun: true}).Model(&User{}).Find(&User{}, user.ID)
+
+	if regexp.MustCompile("SELECT .*name.* FROM .*users").MatchString(result.Statement.SQL.String()) {
+		t.Fatalf("SQL should not include selected names, but got %v", result.Statement.SQL.String())
+	}
+
+	result = DB.Session(&gorm.Session{DryRun: true}).Model(&User{}).Find(&[]User{}, user.ID)
+
+	if regexp.MustCompile("SELECT .*name.* FROM .*users").MatchString(result.Statement.SQL.String()) {
+		t.Fatalf("SQL should not include selected names, but got %v", result.Statement.SQL.String())
+	}
+
+	result = DB.Session(&gorm.Session{DryRun: true}).Model(&User{}).Find(&[]*User{}, user.ID)
+
+	if regexp.MustCompile("SELECT .*name.* FROM .*users").MatchString(result.Statement.SQL.String()) {
+		t.Fatalf("SQL should not include selected names, but got %v", result.Statement.SQL.String())
+	}
 }
 
 func TestNot(t *testing.T) {