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planner: fix a corner case in column pruning rule (#10974) #11020

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Jul 2, 2019
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planner: fix a corner case in column pruning rule (#10974) #11020

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f42e528
planner: fix a corner case in column pruning rule (#10974)
bb7133 Jul 1, 2019
a9f3878
Merge branch 'release-3.0' into bb7133/cherry-pick_10974_3.0
ngaut Jul 2, 2019
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29 changes: 29 additions & 0 deletions cmd/explaintest/r/explain_easy.result
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Original file line number Diff line number Diff line change
Expand Up @@ -192,6 +192,35 @@ HashAgg_18 24000.00 root group by:c1, funcs:firstrow(join_agg_0)
└─IndexReader_62 8000.00 root index:StreamAgg_53
└─StreamAgg_53 8000.00 cop group by:test.t2.c1, funcs:firstrow(test.t2.c1), firstrow(test.t2.c1)
└─IndexScan_60 10000.00 cop table:t2, index:c1, range:[NULL,+inf], keep order:true, stats:pseudo
explain select count(1) from (select count(1) from (select * from t1 where c3 = 100) k) k2;
id count task operator info
StreamAgg_13 1.00 root funcs:count(1)
└─StreamAgg_28 1.00 root funcs:firstrow(col_0)
└─TableReader_29 1.00 root data:StreamAgg_17
└─StreamAgg_17 1.00 cop funcs:firstrow(1)
└─Selection_27 10.00 cop eq(test.t1.c3, 100)
└─TableScan_26 10000.00 cop table:t1, range:[-inf,+inf], keep order:false, stats:pseudo
explain select 1 from (select count(c2), count(c3) from t1) k;
id count task operator info
Projection_5 1.00 root 1
└─StreamAgg_17 1.00 root funcs:firstrow(col_0)
└─TableReader_18 1.00 root data:StreamAgg_9
└─StreamAgg_9 1.00 cop funcs:firstrow(1)
└─TableScan_16 10000.00 cop table:t1, range:[-inf,+inf], keep order:false, stats:pseudo
explain select count(1) from (select max(c2), count(c3) as m from t1) k;
id count task operator info
StreamAgg_11 1.00 root funcs:count(1)
└─StreamAgg_23 1.00 root funcs:firstrow(col_0)
└─TableReader_24 1.00 root data:StreamAgg_15
└─StreamAgg_15 1.00 cop funcs:firstrow(1)
└─TableScan_22 10000.00 cop table:t1, range:[-inf,+inf], keep order:false, stats:pseudo
explain select count(1) from (select count(c2) from t1 group by c3) k;
id count task operator info
StreamAgg_11 1.00 root funcs:count(1)
└─HashAgg_23 8000.00 root group by:col_1, funcs:firstrow(col_0)
└─TableReader_24 8000.00 root data:HashAgg_20
└─HashAgg_20 8000.00 cop group by:test.t1.c3, funcs:firstrow(1)
└─TableScan_15 10000.00 cop table:t1, range:[-inf,+inf], keep order:false, stats:pseudo
set @@session.tidb_opt_insubq_to_join_and_agg=0;
explain select sum(t1.c1 in (select c1 from t2)) from t1;
id count task operator info
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6 changes: 6 additions & 0 deletions cmd/explaintest/t/explain_easy.test
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Expand Up @@ -35,6 +35,12 @@ explain select if(10, t1.c1, t1.c2) from t1;
explain select c1 from t2 union select c1 from t2 union all select c1 from t2;
explain select c1 from t2 union all select c1 from t2 union select c1 from t2;

# https://github.com/pingcap/tidb/issues/9125
explain select count(1) from (select count(1) from (select * from t1 where c3 = 100) k) k2;
explain select 1 from (select count(c2), count(c3) from t1) k;
explain select count(1) from (select max(c2), count(c3) as m from t1) k;
explain select count(1) from (select count(c2) from t1 group by c3) k;

set @@session.tidb_opt_insubq_to_join_and_agg=0;

explain select sum(t1.c1 in (select c1 from t2)) from t1;
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18 changes: 18 additions & 0 deletions planner/core/logical_plan_test.go
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Expand Up @@ -1148,6 +1148,24 @@ func (s *testPlanSuite) TestColumnPruning(c *C) {
12: {"test.t4.a"},
},
},
{
sql: "select 1 from (select count(b) as cnt from t) t1;",
ans: map[int][]string{
1: {"test.t.a"},
},
},
{
sql: "select count(1) from (select count(b) as cnt from t) t1;",
ans: map[int][]string{
1: {"test.t.a"},
},
},
{
sql: "select count(1) from (select count(b) as cnt from t group by c) t1;",
ans: map[int][]string{
1: {"test.t.c"},
},
},
}
for _, tt := range tests {
comment := Commentf("for %s", tt.sql)
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17 changes: 17 additions & 0 deletions planner/core/rule_column_pruning.go
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Expand Up @@ -20,7 +20,9 @@ import (
"github.com/pingcap/parser/model"
"github.com/pingcap/parser/mysql"
"github.com/pingcap/tidb/expression"
"github.com/pingcap/tidb/expression/aggregation"
"github.com/pingcap/tidb/infoschema"
"github.com/pingcap/tidb/types"
)

type columnPruner struct {
Expand Down Expand Up @@ -117,6 +119,21 @@ func (la *LogicalAggregation) PruneColumns(parentUsedCols []*expression.Column)
for _, aggrFunc := range la.AggFuncs {
selfUsedCols = expression.ExtractColumnsFromExpressions(selfUsedCols, aggrFunc.Args, nil)
}
if len(la.AggFuncs) == 0 {
// If all the aggregate functions are pruned, we should add an aggregate function to keep the correctness.
one, err := aggregation.NewAggFuncDesc(la.ctx, ast.AggFuncFirstRow, []expression.Expression{expression.One}, false)
if err != nil {
return err
}
la.AggFuncs = []*aggregation.AggFuncDesc{one}
col := &expression.Column{
ColName: model.NewCIStr("dummy_agg"),
UniqueID: la.ctx.GetSessionVars().AllocPlanColumnID(),
RetType: types.NewFieldType(mysql.TypeLonglong),
}
la.schema.Columns = []*expression.Column{col}
}

if len(la.GroupByItems) > 0 {
for i := len(la.GroupByItems) - 1; i >= 0; i-- {
cols := expression.ExtractColumns(la.GroupByItems[i])
Expand Down