planner: disable projection elimination for select plan of update (#1…

…0962)
pingcap · Jul 15, 2019 · 3f1d234 · 3f1d234
1 parent d420a1f
commit 3f1d234
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Showing 2 changed files with 18 additions and 1 deletion.
diff --git a/planner/core/cbo_test.go b/planner/core/cbo_test.go
@@ -1090,3 +1090,18 @@ func (s *testAnalyzeSuite) TestLimitCrossEstimation(c *C) {
 		"      └─TableScan_19 6.00 cop table:t, keep order:false",
 	))
 }
+
+func (s *testAnalyzeSuite) TestUpdateProjEliminate(c *C) {
+	store, dom, err := newStoreWithBootstrap()
+	c.Assert(err, IsNil)
+	tk := testkit.NewTestKit(c, store)
+	defer func() {
+		dom.Close()
+		store.Close()
+	}()
+
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t(a int, b int)")
+	tk.MustExec("explain update t t1, (select distinct b from t) t2 set t1.b = t2.b")
+}
diff --git a/planner/core/logical_plan_builder.go b/planner/core/logical_plan_builder.go
@@ -2576,7 +2576,9 @@ func (b *PlanBuilder) buildUpdate(update *ast.UpdateStmt) (Plan, error) {
 
 	updt := Update{OrderedList: orderedList}.Init(b.ctx)
 	updt.SetSchema(p.Schema())
-	updt.SelectPlan, err = DoOptimize(b.optFlag, p)
+	// We cannot apply projection elimination when building the subplan, because
+	// columns in orderedList cannot be resolved.
+	updt.SelectPlan, err = DoOptimize(b.optFlag&^flagEliminateProjection, p)
 	if err != nil {
 		return nil, err
 	}