From 6800748915d6d206e33c5cb26e121ba56e4f0d0c Mon Sep 17 00:00:00 2001
From: Chao Wang <cclcwangchao@hotmail.com>
Date: Tue, 6 Jul 2021 13:25:21 +0800
Subject: [PATCH] *: Support create local temporary table if not exist

---
 ddl/db_integration_test.go | 6 ++++++
 executor/ddl.go            | 9 ++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/ddl/db_integration_test.go b/ddl/db_integration_test.go
index 5420de5855391..0cc98f6ef35e6 100644
--- a/ddl/db_integration_test.go
+++ b/ddl/db_integration_test.go
@@ -2825,6 +2825,12 @@ func (s *testIntegrationSuite3) TestCreateTemporaryTable(c *C) {
 	tk.MustExec("rollback")
 	tk.MustQuery("select * from check_data").Check(testkit.Rows())
 
+	// Check create temporary table for if not exists
+	tk.MustExec("create temporary table b_local_temp_table (id int)")
+	_, err = tk.Exec("create temporary table b_local_temp_table (id int)")
+	c.Assert(infoschema.ErrTableExists.Equal(err), IsTrue)
+	tk.MustExec("create temporary table if not exists b_local_temp_table (id int)")
+
 	// Stale read see the local temporary table but can't read on it.
 	tk.MustExec("START TRANSACTION READ ONLY AS OF TIMESTAMP NOW(3)")
 	tk.MustGetErrMsg("select * from overlap", "can not stale read temporary table")
diff --git a/executor/ddl.go b/executor/ddl.go
index 500d7ea70c001..1398cead232a9 100644
--- a/executor/ddl.go
+++ b/executor/ddl.go
@@ -256,7 +256,14 @@ func (e *DDLExec) createSessionTemporaryTable(s *ast.CreateTableStmt) error {
 		sessVars.LocalTemporaryTables = infoschema.NewLocalTemporaryTables()
 	}
 	localTempTables := sessVars.LocalTemporaryTables.(*infoschema.LocalTemporaryTables)
-	return localTempTables.AddTable(dbInfo, tbl)
+	err = localTempTables.AddTable(dbInfo, tbl)
+
+	if err != nil && s.IfNotExists && infoschema.ErrTableExists.Equal(err) {
+		e.ctx.GetSessionVars().StmtCtx.AppendNote(err)
+		return nil
+	}
+
+	return err
 }
 
 func (e *DDLExec) executeCreateView(s *ast.CreateViewStmt) error {