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planner: disable projection elimination for select plan of update #10962

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merged 4 commits into from
Jul 15, 2019
Merged

planner: disable projection elimination for select plan of update #10962

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37b3f7a
planner: disable projection elimination for select plan of update
eurekaka Jun 23, 2019
c0d1a68
Merge branch 'master' into proj_elim
eurekaka Jun 27, 2019
70e3608
Merge branch 'master' into proj_elim
eurekaka Jul 15, 2019
dd39188
Merge branch 'master' into proj_elim
zz-jason Jul 15, 2019
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15 changes: 15 additions & 0 deletions planner/core/cbo_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -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")
}
4 changes: 3 additions & 1 deletion planner/core/logical_plan_builder.go
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Expand Up @@ -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)
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I'm not sure whether there will be some bugs if we disable the projection elimination rule. As you mentioned in the PR description that "The root cause of the error is that during projection elimination, we do not resolve columns in OrderedList field of Update", can we fix this issue in the projection elimination rule for the Update operator?

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Then we need to pass an additional parameter of type Assignment to DoOptimize, it is pretty ugly and ad-hoc IMHO.

if err != nil {
return nil, err
}
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