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planner: eliminate empty projection below aggregation (#29606) (#29635)
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close pingcap/tiflash#3389
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@ti-srebot
ti-srebot authored Dec 19, 2021
1 parent c5ca06c commit 73fafb1
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Showing 3 changed files with 91 additions and 55 deletions.
26 changes: 26 additions & 0 deletions planner/core/logical_plan_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -602,6 +602,9 @@ func (s *testPlanSuite) TestProjectionEliminator(c *C) {
{
sql: "select 1+num from (select 1+a as num from t) t1;",
best: "DataScan(t)->Projection",
}, {
sql: "select count(*) from t where a in (select b from t2 where a is null);",
best: "Join{DataScan(t)->Dual->Aggr(firstrow(test.t2.b))}(test.t.a,test.t2.b)->Aggr(count(1))->Projection",
},
}

Expand All @@ -619,6 +622,29 @@ func (s *testPlanSuite) TestProjectionEliminator(c *C) {
}
}

func (s *testPlanSuite) TestCS3389(c *C) {
defer testleak.AfterTest(c)()

ctx := context.Background()
stmt, err := s.ParseOneStmt("select count(*) from t where a in (select b from t2 where a is null);", "", "")
c.Assert(err, IsNil)
p, _, err := BuildLogicalPlan(ctx, s.ctx, stmt, s.is)
c.Assert(err, IsNil)
p, err = logicalOptimize(context.TODO(), flagBuildKeyInfo|flagPrunColumns|flagPrunColumnsAgain|flagEliminateProjection|flagJoinReOrder, p.(LogicalPlan))
c.Assert(err, IsNil)

// Assert that all Projection is not empty and there is no Projection between Aggregation and Join.
proj, isProj := p.(*LogicalProjection)
c.Assert(isProj, IsTrue)
c.Assert(len(proj.Exprs) > 0, IsTrue)
child := proj.Children()[0]
agg, isAgg := child.(*LogicalAggregation)
c.Assert(isAgg, IsTrue)
child = agg.Children()[0]
_, isJoin := child.(*LogicalJoin)
c.Assert(isJoin, IsTrue)
}

func (s *testPlanSuite) TestAllocID(c *C) {
ctx := MockContext()
pA := DataSource{}.Init(ctx, 0)
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16 changes: 15 additions & 1 deletion planner/core/rule_column_pruning.go
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Original file line number Diff line number Diff line change
Expand Up @@ -147,7 +147,21 @@ func (la *LogicalAggregation) PruneColumns(parentUsedCols []*expression.Column)
la.GroupByItems = []expression.Expression{expression.NewOne()}
}
}
return child.PruneColumns(selfUsedCols)
err := child.PruneColumns(selfUsedCols)
if err != nil {
return err
}
// Do an extra Projection Elimination here. This is specially for empty Projection below Aggregation.
// This kind of Projection would cause some bugs for MPP plan and is safe to be removed.
// This kind of Projection should be removed in Projection Elimination, but currently PrunColumnsAgain is
// the last rule. So we specially handle this case here.
if childProjection, isProjection := child.(*LogicalProjection); isProjection {
if len(childProjection.Exprs) == 0 && childProjection.Schema().Len() == 0 {
childOfChild := childProjection.children[0]
la.SetChildren(childOfChild)
}
}
return nil
}

func pruneByItems(old []*util.ByItems) (new []*util.ByItems, parentUsedCols []*expression.Column) {
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104 changes: 50 additions & 54 deletions planner/core/testdata/integration_serial_suite_out.json
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Original file line number Diff line number Diff line change
Expand Up @@ -67,59 +67,56 @@
{
"SQL": "explain format = 'brief' select count(*) from fact_t, d1_t where fact_t.d1_k = d1_t.d1_k",
"Plan": [
"HashAgg 1.00 root funcs:count(Column#12)->Column#11",
"└─TableReader 1.00 root data:ExchangeSender",
" └─ExchangeSender 1.00 batchCop[tiflash] ExchangeType: PassThrough",
" └─HashAgg 1.00 batchCop[tiflash] funcs:count(1)->Column#12",
" └─HashJoin 8.00 batchCop[tiflash] inner join, equal:[eq(test.d1_t.d1_k, test.fact_t.d1_k)]",
" ├─ExchangeReceiver(Build) 2.00 batchCop[tiflash] ",
" │ └─ExchangeSender 2.00 batchCop[tiflash] ExchangeType: Broadcast",
" │ └─Selection 2.00 batchCop[tiflash] not(isnull(test.d1_t.d1_k))",
" │ └─TableFullScan 2.00 batchCop[tiflash] table:d1_t keep order:false",
" └─Selection(Probe) 8.00 batchCop[tiflash] not(isnull(test.fact_t.d1_k))",
" └─TableFullScan 8.00 batchCop[tiflash] table:fact_t keep order:false"
"StreamAgg 1.00 root funcs:count(1)->Column#11",
"└─TableReader 8.00 root data:ExchangeSender",
" └─ExchangeSender 8.00 cop[tiflash] ExchangeType: PassThrough",
" └─HashJoin 8.00 cop[tiflash] inner join, equal:[eq(test.d1_t.d1_k, test.fact_t.d1_k)]",
" ├─ExchangeReceiver(Build) 2.00 cop[tiflash] ",
" │ └─ExchangeSender 2.00 cop[tiflash] ExchangeType: Broadcast",
" │ └─Selection 2.00 cop[tiflash] not(isnull(test.d1_t.d1_k))",
" │ └─TableFullScan 2.00 cop[tiflash] table:d1_t keep order:false",
" └─Selection(Probe) 8.00 cop[tiflash] not(isnull(test.fact_t.d1_k))",
" └─TableFullScan 8.00 cop[tiflash] table:fact_t keep order:false"
]
},
{
"SQL": "explain format = 'brief' select count(*) from fact_t, d1_t, d2_t, d3_t where fact_t.d1_k = d1_t.d1_k and fact_t.d2_k = d2_t.d2_k and fact_t.d3_k = d3_t.d3_k",
"Plan": [
"HashAgg 1.00 root funcs:count(Column#18)->Column#17",
"└─TableReader 1.00 root data:ExchangeSender",
" └─ExchangeSender 1.00 batchCop[tiflash] ExchangeType: PassThrough",
" └─HashAgg 1.00 batchCop[tiflash] funcs:count(1)->Column#18",
" └─HashJoin 8.00 batchCop[tiflash] inner join, equal:[eq(test.fact_t.d3_k, test.d3_t.d3_k)]",
" ├─ExchangeReceiver(Build) 2.00 batchCop[tiflash] ",
" │ └─ExchangeSender 2.00 batchCop[tiflash] ExchangeType: Broadcast",
" │ └─Selection 2.00 batchCop[tiflash] not(isnull(test.d3_t.d3_k))",
" │ └─TableFullScan 2.00 batchCop[tiflash] table:d3_t keep order:false",
" └─HashJoin(Probe) 8.00 batchCop[tiflash] inner join, equal:[eq(test.fact_t.d2_k, test.d2_t.d2_k)]",
" ├─ExchangeReceiver(Build) 2.00 batchCop[tiflash] ",
" │ └─ExchangeSender 2.00 batchCop[tiflash] ExchangeType: Broadcast",
" │ └─Selection 2.00 batchCop[tiflash] not(isnull(test.d2_t.d2_k))",
" │ └─TableFullScan 2.00 batchCop[tiflash] table:d2_t keep order:false",
" └─HashJoin(Probe) 8.00 batchCop[tiflash] inner join, equal:[eq(test.d1_t.d1_k, test.fact_t.d1_k)]",
" ├─ExchangeReceiver(Build) 2.00 batchCop[tiflash] ",
" │ └─ExchangeSender 2.00 batchCop[tiflash] ExchangeType: Broadcast",
" │ └─Selection 2.00 batchCop[tiflash] not(isnull(test.d1_t.d1_k))",
" │ └─TableFullScan 2.00 batchCop[tiflash] table:d1_t keep order:false",
" └─Selection(Probe) 8.00 batchCop[tiflash] not(isnull(test.fact_t.d1_k)), not(isnull(test.fact_t.d2_k)), not(isnull(test.fact_t.d3_k))",
" └─TableFullScan 8.00 batchCop[tiflash] table:fact_t keep order:false"
"StreamAgg 1.00 root funcs:count(1)->Column#17",
"└─TableReader 8.00 root data:ExchangeSender",
" └─ExchangeSender 8.00 cop[tiflash] ExchangeType: PassThrough",
" └─HashJoin 8.00 cop[tiflash] inner join, equal:[eq(test.fact_t.d3_k, test.d3_t.d3_k)]",
" ├─ExchangeReceiver(Build) 2.00 cop[tiflash] ",
" │ └─ExchangeSender 2.00 cop[tiflash] ExchangeType: Broadcast",
" │ └─Selection 2.00 cop[tiflash] not(isnull(test.d3_t.d3_k))",
" │ └─TableFullScan 2.00 cop[tiflash] table:d3_t keep order:false",
" └─HashJoin(Probe) 8.00 cop[tiflash] inner join, equal:[eq(test.fact_t.d2_k, test.d2_t.d2_k)]",
" ├─ExchangeReceiver(Build) 2.00 cop[tiflash] ",
" │ └─ExchangeSender 2.00 cop[tiflash] ExchangeType: Broadcast",
" │ └─Selection 2.00 cop[tiflash] not(isnull(test.d2_t.d2_k))",
" │ └─TableFullScan 2.00 cop[tiflash] table:d2_t keep order:false",
" └─HashJoin(Probe) 8.00 cop[tiflash] inner join, equal:[eq(test.d1_t.d1_k, test.fact_t.d1_k)]",
" ├─ExchangeReceiver(Build) 2.00 cop[tiflash] ",
" │ └─ExchangeSender 2.00 cop[tiflash] ExchangeType: Broadcast",
" │ └─Selection 2.00 cop[tiflash] not(isnull(test.d1_t.d1_k))",
" │ └─TableFullScan 2.00 cop[tiflash] table:d1_t keep order:false",
" └─Selection(Probe) 8.00 cop[tiflash] not(isnull(test.fact_t.d1_k)), not(isnull(test.fact_t.d2_k)), not(isnull(test.fact_t.d3_k))",
" └─TableFullScan 8.00 cop[tiflash] table:fact_t keep order:false"
]
},
{
"SQL": "explain format = 'brief' select count(*) from fact_t, d1_t where fact_t.d1_k = d1_t.d1_k",
"Plan": [
"HashAgg 1.00 root funcs:count(Column#12)->Column#11",
"└─TableReader 1.00 root data:ExchangeSender",
" └─ExchangeSender 1.00 batchCop[tiflash] ExchangeType: PassThrough",
" └─HashAgg 1.00 batchCop[tiflash] funcs:count(1)->Column#12",
" └─HashJoin 8.00 batchCop[tiflash] inner join, equal:[eq(test.d1_t.d1_k, test.fact_t.d1_k)]",
" ├─ExchangeReceiver(Build) 2.00 batchCop[tiflash] ",
" │ └─ExchangeSender 2.00 batchCop[tiflash] ExchangeType: Broadcast",
" │ └─Selection 2.00 batchCop[tiflash] not(isnull(test.d1_t.d1_k))",
" │ └─TableFullScan 2.00 batchCop[tiflash] table:d1_t keep order:false",
" └─Selection(Probe) 8.00 batchCop[tiflash] not(isnull(test.fact_t.d1_k))",
" └─TableFullScan 8.00 batchCop[tiflash] table:fact_t keep order:false"
"StreamAgg 1.00 root funcs:count(1)->Column#11",
"└─TableReader 8.00 root data:ExchangeSender",
" └─ExchangeSender 8.00 cop[tiflash] ExchangeType: PassThrough",
" └─HashJoin 8.00 cop[tiflash] inner join, equal:[eq(test.d1_t.d1_k, test.fact_t.d1_k)]",
" ├─ExchangeReceiver(Build) 2.00 cop[tiflash] ",
" │ └─ExchangeSender 2.00 cop[tiflash] ExchangeType: Broadcast",
" │ └─Selection 2.00 cop[tiflash] not(isnull(test.d1_t.d1_k))",
" │ └─TableFullScan 2.00 cop[tiflash] table:d1_t keep order:false",
" └─Selection(Probe) 8.00 cop[tiflash] not(isnull(test.fact_t.d1_k))",
" └─TableFullScan 8.00 cop[tiflash] table:fact_t keep order:false"
]
},
{
Expand Down Expand Up @@ -153,17 +150,16 @@
{
"SQL": "explain format = 'brief' select count(*) from fact_t join d1_t on fact_t.d1_k = d1_t.d1_k and fact_t.col1 > d1_t.value",
"Plan": [
"HashAgg 1.00 root funcs:count(Column#12)->Column#11",
"└─TableReader 1.00 root data:ExchangeSender",
" └─ExchangeSender 1.00 batchCop[tiflash] ExchangeType: PassThrough",
" └─HashAgg 1.00 batchCop[tiflash] funcs:count(1)->Column#12",
" └─HashJoin 8.00 batchCop[tiflash] inner join, equal:[eq(test.d1_t.d1_k, test.fact_t.d1_k)], other cond:gt(test.fact_t.col1, test.d1_t.value)",
" ├─ExchangeReceiver(Build) 2.00 batchCop[tiflash] ",
" │ └─ExchangeSender 2.00 batchCop[tiflash] ExchangeType: Broadcast",
" │ └─Selection 2.00 batchCop[tiflash] not(isnull(test.d1_t.d1_k)), not(isnull(test.d1_t.value))",
" │ └─TableFullScan 2.00 batchCop[tiflash] table:d1_t keep order:false",
" └─Selection(Probe) 8.00 batchCop[tiflash] not(isnull(test.fact_t.col1)), not(isnull(test.fact_t.d1_k))",
" └─TableFullScan 8.00 batchCop[tiflash] table:fact_t keep order:false"
"StreamAgg 1.00 root funcs:count(1)->Column#11",
"└─TableReader 8.00 root data:ExchangeSender",
" └─ExchangeSender 8.00 cop[tiflash] ExchangeType: PassThrough",
" └─HashJoin 8.00 cop[tiflash] inner join, equal:[eq(test.d1_t.d1_k, test.fact_t.d1_k)], other cond:gt(test.fact_t.col1, test.d1_t.value)",
" ├─ExchangeReceiver(Build) 2.00 cop[tiflash] ",
" │ └─ExchangeSender 2.00 cop[tiflash] ExchangeType: Broadcast",
" │ └─Selection 2.00 cop[tiflash] not(isnull(test.d1_t.d1_k)), not(isnull(test.d1_t.value))",
" │ └─TableFullScan 2.00 cop[tiflash] table:d1_t keep order:false",
" └─Selection(Probe) 8.00 cop[tiflash] not(isnull(test.fact_t.col1)), not(isnull(test.fact_t.d1_k))",
" └─TableFullScan 8.00 cop[tiflash] table:fact_t keep order:false"
]
},
{
Expand Down

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