feat(PreparedStmtDB): support reset (#5782)

* feat(PreparedStmtDB): support reset

* fix: close all stmt

* test: fix test

* fix: delete one by one

prepare_stmt.go

@@ -44,6 +44,18 @@ func (db *PreparedStmtDB) Close() {
 	}
 }
 
+func (db *PreparedStmtDB) Reset() {
+	db.Mux.Lock()
+	defer db.Mux.Unlock()
+	for query, stmt := range db.Stmts {
+		delete(db.Stmts, query)
+		go stmt.Close()
+	}
+
+	db.PreparedSQL = make([]string, 0, 100)
+	db.Stmts = map[string](*Stmt){}
+}
+
 func (db *PreparedStmtDB) prepare(ctx context.Context, conn ConnPool, isTransaction bool, query string) (Stmt, error) {
 	db.Mux.RLock()
 	if stmt, ok := db.Stmts[query]; ok && (!stmt.Transaction || isTransaction) {

tests/prepared_stmt_test.go

@@ -2,8 +2,8 @@ package tests_test
 
 import (
 	"context"
-	"sync"
 	"errors"
+	"sync"
 	"testing"
 	"time"
 
@@ -168,3 +168,29 @@ func TestPreparedStmtInTransaction(t *testing.T) {
 		t.Errorf("Failed, got error: %v", err)
 	}
 }
+
+func TestPreparedStmtReset(t *testing.T) {
+	tx := DB.Session(&gorm.Session{PrepareStmt: true})
+
+	user := *GetUser("prepared_stmt_reset", Config{})
+	tx = tx.Create(&user)
+
+	pdb, ok := tx.ConnPool.(*gorm.PreparedStmtDB)
+	if !ok {
+		t.Fatalf("should assign PreparedStatement Manager back to database when using PrepareStmt mode")
+	}
+
+	pdb.Mux.Lock()
+	if len(pdb.Stmts) == 0 {
+		pdb.Mux.Unlock()
+		t.Fatalf("prepared stmt can not be empty")
+	}
+	pdb.Mux.Unlock()
+
+	pdb.Reset()
+	pdb.Mux.Lock()
+	defer pdb.Mux.Unlock()
+	if len(pdb.Stmts) != 0 {
+		t.Fatalf("prepared stmt should be empty")
+	}
+}