fix: prepare deadlock

prepare_stmt.go

@@ -50,23 +50,18 @@ func (db *PreparedStmtDB) prepare(ctx context.Context, conn ConnPool, isTransact
 	}
 	db.Mux.RUnlock()
 
-	db.Mux.Lock()
-	defer db.Mux.Unlock()
-
-	// double check
-	if stmt, ok := db.Stmts[query]; ok && (!stmt.Transaction || isTransaction) {
-		return stmt, nil
-	} else if ok {
-		go stmt.Close()
-	}
-
 	stmt, err := conn.PrepareContext(ctx, query)
-	if err == nil {
+	if err != nil {
-		db.Stmts[query] = Stmt{Stmt: stmt, Transaction: isTransaction}
+		return Stmt{}, err
-		db.PreparedSQL = append(db.PreparedSQL, query)
 	}
 
-	return db.Stmts[query], err
+	cacheStmt := Stmt{Stmt: stmt, Transaction: isTransaction}
+	db.Mux.Lock()
+	db.Stmts[query] = cacheStmt
+	db.PreparedSQL = append(db.PreparedSQL, query)
+	db.Mux.Unlock()
+
+	return cacheStmt, err
 }
 
 func (db *PreparedStmtDB) BeginTx(ctx context.Context, opt *sql.TxOptions) (ConnPool, error) {

tests/prepared_stmt_test.go

@@ -2,6 +2,7 @@ package tests_test
 
 import (
 	"context"
+	"sync"
 	"testing"
 	"time"
 
@@ -88,3 +89,27 @@ func TestPreparedStmtFromTransaction(t *testing.T) {
 	}
 	tx2.Commit()
 }
+
+func TestPreparedStmtDeadlock(t *testing.T) {
+	tx, err := OpenTestConnection()
+	AssertEqual(t, err, nil)
+
+	sqlDB, _ := tx.DB()
+	sqlDB.SetMaxOpenConns(1)
+
+	tx = tx.Session(&gorm.Session{PrepareStmt: true})
+
+	wg := sync.WaitGroup{}
+	for i := 0; i < 2; i++ {
+		wg.Add(1)
+		go func(j int) {
+			user := User{Name: "jinzhu"}
+			tx.Create(&user)
+
+			var result User
+			tx.First(&result)
+			wg.Done()
+		}(i)
+	}
+	wg.Wait()
+}