copr: fix copr cache panic when tidb_enable_collect_execution_info …

…is off (#48340) (#48475)

close #48212

executor/distsql_test.go

@@ -699,3 +699,25 @@ func TestCoprocessorBatchByStore(t *testing.T) {
 		}
 	}
 }
+
+func TestCoprCacheWithoutExecutionInfo(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk1 := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t(id int)")
+	tk.MustExec("insert into t values(1), (2), (3)")
+
+	require.NoError(t, failpoint.Enable("github.com/pingcap/tidb/store/mockstore/unistore/cophandler/mockCopCacheInUnistore", `return(123)`))
+	defer func() {
+		require.NoError(t, failpoint.Disable("github.com/pingcap/tidb/store/mockstore/unistore/cophandler/mockCopCacheInUnistore"))
+	}()
+
+	defer tk.MustExec("set @@tidb_enable_collect_execution_info=1")
+	ctx := context.WithValue(context.Background(), "CheckSelectRequestHook", func(_ *kv.Request) {
+		tk1.MustExec("set @@tidb_enable_collect_execution_info=0")
+	})
+	tk.MustQuery("select * from t").Check(testkit.Rows("1", "2", "3"))
+	tk.MustQueryWithContext(ctx, "select * from t").Check(testkit.Rows("1", "2", "3"))
+}

store/copr/coprocessor.go

@@ -1637,7 +1637,14 @@ func (worker *copIteratorWorker) handleCopCache(task *copTask, resp *copResponse
 				resp.pbResp.Range = nil
 			}
 		}
-		resp.detail.CoprCacheHit = true
+		// `worker.enableCollectExecutionInfo` is loaded from the instance's config. Because it's not related to the request,
+		// the cache key can be same when `worker.enableCollectExecutionInfo` is true or false.
+		// When `worker.enableCollectExecutionInfo` is false, the `resp.detail` is nil, and hit cache is still possible.
+		// Check `resp.detail` to avoid panic.
+		// Details: https://github.com/pingcap/tidb/issues/48212
+		if resp.detail != nil {
+			resp.detail.CoprCacheHit = true
+		}
 		return nil
 	}
 	copr_metrics.CoprCacheCounterMiss.Add(1)