Setup DB's ConnPool in PrepareStmt mode, fix #3362

gorm.go

@@ -176,6 +176,8 @@ func (db *DB) Session(config *Session) *DB {
 				Mux:      preparedStmt.Mux,
 				Stmts:    preparedStmt.Stmts,
 			}
+			txConfig.ConnPool = tx.Statement.ConnPool
+			txConfig.PrepareStmt = true
 		}
 	}
 

tests/prepared_stmt_test.go

@@ -12,6 +12,10 @@ import (
 func TestPreparedStmt(t *testing.T) {
 	tx := DB.Session(&gorm.Session{PrepareStmt: true})
 
+	if _, ok := tx.ConnPool.(*gorm.PreparedStmtDB); !ok {
+		t.Fatalf("should assign PreparedStatement Manager back to database when using PrepareStmt mode")
+	}
+
 	ctx, cancel := context.WithTimeout(context.Background(), 500*time.Millisecond)
 	defer cancel()
 	txCtx := tx.WithContext(ctx)