From 8b970d7d41f6d680036304feea22ac72de7cd094 Mon Sep 17 00:00:00 2001
From: HuaiyuXu <391585975@qq.com>
Date: Wed, 26 Dec 2018 11:00:06 +0800
Subject: [PATCH] planner: fix a sporadic panic due to the PR #7684 when using
 the prepared plan cache (#7956) (#8826)

---
 executor/prepared.go | 4 ++++
 tidb-server/main.go  | 3 ++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/executor/prepared.go b/executor/prepared.go
index bb886b9f26721..4cd28f1c7679d 100644
--- a/executor/prepared.go
+++ b/executor/prepared.go
@@ -128,6 +128,10 @@ func (e *PrepareExec) Next(ctx context.Context, chk *chunk.Chunk) error {
 	if _, ok := stmt.(ast.DDLNode); ok {
 		return ErrPrepareDDL
 	}
+	err = ResetContextOfStmt(e.ctx, stmt)
+	if err != nil {
+		return err
+	}
 	var extractor paramMarkerExtractor
 	stmt.Accept(&extractor)
 
diff --git a/tidb-server/main.go b/tidb-server/main.go
index c03a10ad6fe72..02fe72c9740f2 100644
--- a/tidb-server/main.go
+++ b/tidb-server/main.go
@@ -405,7 +405,8 @@ func setGlobalVars() {
 	variable.SysVars[variable.TIDBMemQuotaQuery].Value = strconv.FormatInt(cfg.MemQuotaQuery, 10)
 	variable.SysVars["lower_case_table_names"].Value = strconv.Itoa(cfg.LowerCaseTableNames)
 
-	plannercore.SetPreparedPlanCache(cfg.PreparedPlanCache.Enabled)
+	// For CI environment we default enable prepare-plan-cache.
+	plannercore.SetPreparedPlanCache(config.CheckTableBeforeDrop || cfg.PreparedPlanCache.Enabled)
 	if plannercore.PreparedPlanCacheEnabled() {
 		plannercore.PreparedPlanCacheCapacity = cfg.PreparedPlanCache.Capacity
 	}