From f87bfe8c31b7a44fc5fcfae7cc847ab4ed5b21e4 Mon Sep 17 00:00:00 2001
From: a631807682 <631807682@qq.com>
Date: Sat, 13 Aug 2022 10:43:37 +0800
Subject: [PATCH] fix: double check prepare

---
 prepare_stmt.go | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/prepare_stmt.go b/prepare_stmt.go
index 360b06a8..456204b8 100644
--- a/prepare_stmt.go
+++ b/prepare_stmt.go
@@ -58,8 +58,20 @@ func (db *PreparedStmtDB) prepare(ctx context.Context, conn ConnPool, isTransact
 	}
 	db.Mux.RUnlock()
 
-	// cache preparing stmt first
 	db.Mux.Lock()
+	// double check
+	if stmt, ok := db.Stmts[query]; ok && (!stmt.Transaction || isTransaction) {
+		db.Mux.Unlock()
+		// wait for other goroutines prepared
+		<-stmt.prepared
+		if stmt.prepareErr != nil {
+			return Stmt{}, stmt.prepareErr
+		}
+
+		return *stmt, nil
+	}
+
+	// cache preparing stmt first
 	cacheStmt := Stmt{Transaction: isTransaction, prepared: make(chan struct{})}
 	db.Stmts[query] = &cacheStmt
 	db.Mux.Unlock()