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planner: fix wrong aggregate pruning for some cases #25289

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merged 3 commits into from
Jun 16, 2021
Merged

planner: fix wrong aggregate pruning for some cases #25289

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a1b83f8
planner: fix wrong aggregate pruning for some cases
lzmhhh123 Jun 9, 2021
8046a06
Merge branch 'master' into bug-fix/fix_prune_agg_col
lzmhhh123 Jun 9, 2021
f4b3cb8
Merge branch 'master' into bug-fix/fix_prune_agg_col
ti-chi-bot Jun 16, 2021
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9 changes: 6 additions & 3 deletions planner/core/rule_column_pruning.go
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Original file line number Diff line number Diff line change
Expand Up @@ -89,13 +89,16 @@ func (la *LogicalAggregation) PruneColumns(parentUsedCols []*expression.Column)
used := expression.GetUsedList(parentUsedCols, la.Schema())

allFirstRow := true
allRemainFirstRow := true
for i := len(used) - 1; i >= 0; i-- {
if la.AggFuncs[i].Name != ast.AggFuncFirstRow {
allFirstRow = false
}
if !used[i] {
la.schema.Columns = append(la.schema.Columns[:i], la.schema.Columns[i+1:]...)
la.AggFuncs = append(la.AggFuncs[:i], la.AggFuncs[i+1:]...)
} else if la.AggFuncs[i].Name != ast.AggFuncFirstRow {
allRemainFirstRow = false
}
}
var selfUsedCols []*expression.Column
Expand All @@ -106,7 +109,7 @@ func (la *LogicalAggregation) PruneColumns(parentUsedCols []*expression.Column)
aggrFunc.OrderByItems, cols = pruneByItems(aggrFunc.OrderByItems)
selfUsedCols = append(selfUsedCols, cols...)
}
if len(la.AggFuncs) == 0 {
if len(la.AggFuncs) == 0 || (!allFirstRow && allRemainFirstRow) {
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Add comments why we need to add this check

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https://github.com/pingcap/tidb/pull/25289/files#diff-ae586e551e5a201a40c83192b7dc23cc2778739ef522fcb02e4fb7fac2125c99R113

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// If all the aggregate functions are pruned, we should add an aggregate function to maintain the info of row numbers.
// For all the aggregate functions except `first_row`, if we have an empty table defined as t(a,b),
// `select agg(a) from t` would always return one row, while `select agg(a) from t group by b` would return empty.
Expand All @@ -121,12 +124,12 @@ func (la *LogicalAggregation) PruneColumns(parentUsedCols []*expression.Column)
if err != nil {
return err
}
la.AggFuncs = []*aggregation.AggFuncDesc{newAgg}
la.AggFuncs = append(la.AggFuncs, newAgg)
col := &expression.Column{
UniqueID: la.ctx.GetSessionVars().AllocPlanColumnID(),
RetType: newAgg.RetTp,
}
la.schema.Columns = []*expression.Column{col}
la.schema.Columns = append(la.schema.Columns, col)
}

if len(la.GroupByItems) > 0 {
Expand Down
22 changes: 11 additions & 11 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 @@ -2225,14 +2225,14 @@
" │ └─Selection 9990.00 batchCop[tiflash] not(isnull(test.t.id))",
" │ └─TableFullScan 10000.00 batchCop[tiflash] table:t keep order:false, stats:pseudo",
" └─Projection(Probe) 7992.00 batchCop[tiflash] Column#11, test.t.id",
" └─HashAgg 7992.00 batchCop[tiflash] group by:Column#32, funcs:sum(Column#30)->Column#11, funcs:firstrow(Column#31)->test.t.id",
" └─Projection 9990.00 batchCop[tiflash] cast(test.t.id, decimal(32,0) BINARY)->Column#30, test.t.id, test.t.id",
" └─HashAgg 7992.00 batchCop[tiflash] group by:Column#39, funcs:sum(Column#37)->Column#11, funcs:firstrow(Column#38)->test.t.id",
" └─Projection 9990.00 batchCop[tiflash] cast(test.t.id, decimal(32,0) BINARY)->Column#37, test.t.id, test.t.id",
" └─HashJoin 9990.00 batchCop[tiflash] inner join, equal:[eq(test.t.id, test.t.id)]",
" ├─Projection(Build) 7992.00 batchCop[tiflash] test.t.id",
" │ └─HashAgg 7992.00 batchCop[tiflash] group by:test.t.id, funcs:firstrow(test.t.id)->test.t.id",
" ├─Projection(Build) 7992.00 batchCop[tiflash] test.t.id, Column#13",
" │ └─HashAgg 7992.00 batchCop[tiflash] group by:test.t.id, funcs:firstrow(test.t.id)->test.t.id, funcs:sum(Column#17)->Column#13",
" │ └─ExchangeReceiver 7992.00 batchCop[tiflash] ",
" │ └─ExchangeSender 7992.00 batchCop[tiflash] ExchangeType: HashPartition, Hash Cols: test.t.id",
" │ └─HashAgg 7992.00 batchCop[tiflash] group by:test.t.id, ",
" │ └─HashAgg 7992.00 batchCop[tiflash] group by:test.t.id, funcs:count(1)->Column#17",
" │ └─Selection 9990.00 batchCop[tiflash] not(isnull(test.t.id))",
" │ └─TableFullScan 10000.00 batchCop[tiflash] table:t keep order:false, stats:pseudo",
" └─ExchangeReceiver(Probe) 9990.00 batchCop[tiflash] ",
Expand Down Expand Up @@ -2479,19 +2479,19 @@
" │ └─Selection 9990.00 batchCop[tiflash] not(isnull(test.t.id))",
" │ └─TableFullScan 10000.00 batchCop[tiflash] table:t keep order:false, stats:pseudo",
" └─Projection(Probe) 7992.00 batchCop[tiflash] Column#11, test.t.id",
" └─HashAgg 7992.00 batchCop[tiflash] group by:test.t.id, funcs:sum(Column#14)->Column#11, funcs:firstrow(test.t.id)->test.t.id",
" └─HashAgg 7992.00 batchCop[tiflash] group by:test.t.id, funcs:sum(Column#17)->Column#11, funcs:firstrow(test.t.id)->test.t.id",
" └─ExchangeReceiver 7992.00 batchCop[tiflash] ",
" └─ExchangeSender 7992.00 batchCop[tiflash] ExchangeType: HashPartition, Hash Cols: test.t.id",
" └─HashAgg 7992.00 batchCop[tiflash] group by:Column#27, funcs:sum(Column#26)->Column#14",
" └─Projection 9990.00 batchCop[tiflash] cast(test.t.id, decimal(32,0) BINARY)->Column#26, test.t.id",
" └─HashAgg 7992.00 batchCop[tiflash] group by:Column#33, funcs:sum(Column#32)->Column#17",
" └─Projection 9990.00 batchCop[tiflash] cast(test.t.id, decimal(32,0) BINARY)->Column#32, test.t.id",
" └─HashJoin 9990.00 batchCop[tiflash] inner join, equal:[eq(test.t.id, test.t.id)]",
" ├─ExchangeReceiver(Build) 7992.00 batchCop[tiflash] ",
" │ └─ExchangeSender 7992.00 batchCop[tiflash] ExchangeType: Broadcast",
" │ └─Projection 7992.00 batchCop[tiflash] test.t.id",
" │ └─HashAgg 7992.00 batchCop[tiflash] group by:test.t.id, funcs:firstrow(test.t.id)->test.t.id",
" │ └─Projection 7992.00 batchCop[tiflash] test.t.id, Column#13",
" │ └─HashAgg 7992.00 batchCop[tiflash] group by:test.t.id, funcs:firstrow(test.t.id)->test.t.id, funcs:sum(Column#16)->Column#13",
" │ └─ExchangeReceiver 7992.00 batchCop[tiflash] ",
" │ └─ExchangeSender 7992.00 batchCop[tiflash] ExchangeType: HashPartition, Hash Cols: test.t.id",
" │ └─HashAgg 7992.00 batchCop[tiflash] group by:test.t.id, ",
" │ └─HashAgg 7992.00 batchCop[tiflash] group by:test.t.id, funcs:count(1)->Column#16",
" │ └─Selection 9990.00 batchCop[tiflash] not(isnull(test.t.id))",
" │ └─TableFullScan 10000.00 batchCop[tiflash] table:t keep order:false, stats:pseudo",
" └─Selection(Probe) 9990.00 batchCop[tiflash] not(isnull(test.t.id))",
Expand Down
3 changes: 2 additions & 1 deletion planner/core/testdata/integration_suite_in.json
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Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,8 @@
"select count(1) from t join (select max(a) from t where false group by a) as tmp",
"select count(1) from t join (select min(a) from t where false group by a) as tmp",
"select count(1) from t join (select sum(a) from t where false group by a) as tmp",
"select count(1) from t join (select avg(a) from t where false group by a) as tmp"
"select count(1) from t join (select avg(a) from t where false group by a) as tmp",
"SELECT avg(2) FROM(SELECT min(c) FROM t JOIN(SELECT 1 c) d ORDER BY a) e"
]
},
{
Expand Down
6 changes: 6 additions & 0 deletions planner/core/testdata/integration_suite_out.json
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Expand Up @@ -126,6 +126,12 @@
"Res": [
"0"
]
},
{
"SQL": "SELECT avg(2) FROM(SELECT min(c) FROM t JOIN(SELECT 1 c) d ORDER BY a) e",
"Res": [
"2.0000"
]
}
]
},
Expand Down